diff --git a/substrate/frame/babe/src/lib.rs b/substrate/frame/babe/src/lib.rs
index dc704b5bcc..209b7eea38 100644
--- a/substrate/frame/babe/src/lib.rs
+++ b/substrate/frame/babe/src/lib.rs
@@ -349,6 +349,9 @@ impl<T: Trait> Module<T> {
 	// -------------- IMPORTANT NOTE --------------
 	// This implementation is linked to how [`should_epoch_change`] is working. This might need to
 	// be updated accordingly, if the underlying mechanics of slot and epochs change.
+	//
+	// WEIGHT NOTE: This function is tied to the weight of `EstimateNextSessionRotation`. If you update
+	// this function, you must also update the corresponding weight.
 	pub fn next_expected_epoch_change(now: T::BlockNumber) -> Option<T::BlockNumber> {
 		let next_slot = Self::current_epoch_start().saturating_add(T::EpochDuration::get());
 		next_slot
@@ -550,6 +553,12 @@ impl<T: Trait> frame_support::traits::EstimateNextSessionRotation<T::BlockNumber
 	fn estimate_next_session_rotation(now: T::BlockNumber) -> Option<T::BlockNumber> {
 		Self::next_expected_epoch_change(now)
 	}
+
+	// The validity of this weight depends on the implementation of `estimate_next_session_rotation`
+	fn weight(_now: T::BlockNumber) -> Weight {
+		// Read: Current Slot, Epoch Index, Genesis Slot
+		T::DbWeight::get().reads(3)
+	}
 }
 
 impl<T: Trait> frame_support::traits::Lateness<T::BlockNumber> for Module<T> {
diff --git a/substrate/frame/session/src/lib.rs b/substrate/frame/session/src/lib.rs
index 8e25221131..167cf8bcdb 100644
--- a/substrate/frame/session/src/lib.rs
+++ b/substrate/frame/session/src/lib.rs
@@ -170,6 +170,14 @@ impl<
 			offset
 		})
 	}
+
+	fn weight(_now: BlockNumber) -> Weight {
+		// Weight note: `estimate_next_session_rotation` has no storage reads and trivial computational overhead.
+		// There should be no risk to the chain having this weight value be zero for now.
+		// However, this value of zero was not properly calculated, and so it would be reasonable
+		// to come back here and properly calculate the weight of this function.
+		0
+	}
 }
 
 /// A trait for managing creation of new validator set.
@@ -785,4 +793,8 @@ impl<T: Trait> EstimateNextNewSession<T::BlockNumber> for Module<T> {
 	fn estimate_next_new_session(now: T::BlockNumber) -> Option<T::BlockNumber> {
 		T::NextSessionRotation::estimate_next_session_rotation(now)
 	}
+
+	fn weight(now: T::BlockNumber) -> Weight {
+		T::NextSessionRotation::weight(now)
+	}
 }
diff --git a/substrate/frame/staking/src/benchmarking.rs b/substrate/frame/staking/src/benchmarking.rs
index 2686623aa1..8c5f70daef 100644
--- a/substrate/frame/staking/src/benchmarking.rs
+++ b/substrate/frame/staking/src/benchmarking.rs
@@ -27,9 +27,11 @@ use frame_system::RawOrigin;
 use frame_benchmarking::{benchmarks, account};
 
 use crate::Module as Staking;
-use frame_system::Module as System;
 
 const SEED: u32 = 0;
+const MAX_SPANS: u32 = 100;
+const MAX_VALIDATORS: u32 = 1000;
+const MAX_SLASHES: u32 = 1000;
 
 fn create_funded_user<T: Trait>(string: &'static str, n: u32) -> T::AccountId {
 	let user = account(string, n, SEED);
@@ -62,6 +64,22 @@ fn create_validators<T: Trait>(max: u32) -> Result<Vec<<T::Lookup as StaticLooku
 	Ok(validators)
 }
 
+// Add slashing spans to a user account. Not relevant for actual use, only to benchmark
+// read and write operations.
+fn add_slashing_spans<T: Trait>(who: &T::AccountId, spans: u32) {
+	if spans == 0 { return }
+
+	// For the first slashing span, we initialize
+	let mut slashing_spans = crate::slashing::SlashingSpans::new(0);
+	SpanSlash::<T>::insert((who, 0), crate::slashing::SpanRecord::default());
+
+	for i in 1 .. spans {
+		assert!(slashing_spans.end_span(i));
+		SpanSlash::<T>::insert((who, i), crate::slashing::SpanRecord::default());
+	}
+	SlashingSpans::<T>::insert(who, slashing_spans);
+}
+
 // This function generates v validators and n nominators who are randomly nominating up to MAX_NOMINATIONS.
 pub fn create_validators_with_nominators_for_era<T: Trait>(v: u32, n: u32) -> Result<(), &'static str> {
 	let mut validators: Vec<<T::Lookup as StaticLookup>::Source> = Vec::with_capacity(v as usize);
@@ -157,46 +175,93 @@ benchmarks! {
 		let u in ...;
 		let stash = create_funded_user::<T>("stash",u);
 		let controller = create_funded_user::<T>("controller", u);
-		let controller_lookup: <T::Lookup as StaticLookup>::Source = T::Lookup::unlookup(controller);
+		let controller_lookup: <T::Lookup as StaticLookup>::Source = T::Lookup::unlookup(controller.clone());
 		let reward_destination = RewardDestination::Staked;
 		let amount = T::Currency::minimum_balance() * 10.into();
-	}: _(RawOrigin::Signed(stash), controller_lookup, amount, reward_destination)
+	}: _(RawOrigin::Signed(stash.clone()), controller_lookup, amount, reward_destination)
+	verify {
+		assert!(Bonded::<T>::contains_key(stash));
+		assert!(Ledger::<T>::contains_key(controller));
+	}
 
 	bond_extra {
 		let u in ...;
-		let (stash, _) = create_stash_controller::<T>(u)?;
+		let (stash, controller) = create_stash_controller::<T>(u)?;
 		let max_additional = T::Currency::minimum_balance() * 10.into();
+		let ledger = Ledger::<T>::get(&controller).ok_or("ledger not created before")?;
+		let original_bonded: BalanceOf<T> = ledger.active;
 	}: _(RawOrigin::Signed(stash), max_additional)
+	verify {
+		let ledger = Ledger::<T>::get(&controller).ok_or("ledger not created after")?;
+		let new_bonded: BalanceOf<T> = ledger.active;
+		assert!(original_bonded < new_bonded);
+	}
 
 	unbond {
 		let u in ...;
 		let (_, controller) = create_stash_controller::<T>(u)?;
 		let amount = T::Currency::minimum_balance() * 10.into();
-	}: _(RawOrigin::Signed(controller), amount)
+		let ledger = Ledger::<T>::get(&controller).ok_or("ledger not created before")?;
+		let original_bonded: BalanceOf<T> = ledger.active;
+	}: _(RawOrigin::Signed(controller.clone()), amount)
+	verify {
+		let ledger = Ledger::<T>::get(&controller).ok_or("ledger not created after")?;
+		let new_bonded: BalanceOf<T> = ledger.active;
+		assert!(original_bonded > new_bonded);
+	}
+
+	// Withdraw only updates the ledger
+	withdraw_unbonded_update {
+		// Slashing Spans
+		let s in 0 .. MAX_SPANS;
+		let (stash, controller) = create_stash_controller::<T>(0)?;
+		add_slashing_spans::<T>(&stash, s);
+		let amount = T::Currency::minimum_balance() * 5.into(); // Half of total
+		Staking::<T>::unbond(RawOrigin::Signed(controller.clone()).into(), amount)?;
+		CurrentEra::put(EraIndex::max_value());
+		let ledger = Ledger::<T>::get(&controller).ok_or("ledger not created before")?;
+		let original_total: BalanceOf<T> = ledger.total;
+	}: withdraw_unbonded(RawOrigin::Signed(controller.clone()), s)
+	verify {
+		let ledger = Ledger::<T>::get(&controller).ok_or("ledger not created after")?;
+		let new_total: BalanceOf<T> = ledger.total;
+		assert!(original_total > new_total);
+	}
 
 	// Worst case scenario, everything is removed after the bonding duration
-	withdraw_unbonded {
-		let u in ...;
-		let (stash, controller) = create_stash_controller::<T>(u)?;
+	withdraw_unbonded_kill {
+		// Slashing Spans
+		let s in 0 .. MAX_SPANS;
+		let (stash, controller) = create_stash_controller::<T>(0)?;
+		add_slashing_spans::<T>(&stash, s);
 		let amount = T::Currency::minimum_balance() * 10.into();
 		Staking::<T>::unbond(RawOrigin::Signed(controller.clone()).into(), amount)?;
-		let current_block = System::<T>::block_number();
-		// let unbond_block = current_block + T::BondingDuration::get().into() + 10.into();
-		// System::<T>::set_block_number(unbond_block);
-	}: _(RawOrigin::Signed(controller))
+		CurrentEra::put(EraIndex::max_value());
+		let ledger = Ledger::<T>::get(&controller).ok_or("ledger not created before")?;
+		let original_total: BalanceOf<T> = ledger.total;
+	}: withdraw_unbonded(RawOrigin::Signed(controller.clone()), s)
+	verify {
+		assert!(!Ledger::<T>::contains_key(controller));
+	}
 
 	validate {
 		let u in ...;
-		let (_, controller) = create_stash_controller::<T>(u)?;
+		let (stash, controller) = create_stash_controller::<T>(u)?;
 		let prefs = ValidatorPrefs::default();
 	}: _(RawOrigin::Signed(controller), prefs)
+	verify {
+		assert!(Validators::<T>::contains_key(stash));
+	}
 
 	// Worst case scenario, MAX_NOMINATIONS
 	nominate {
 		let n in 1 .. MAX_NOMINATIONS as u32;
-		let (_, controller) = create_stash_controller::<T>(n + 1)?;
+		let (stash, controller) = create_stash_controller::<T>(n + 1)?;
 		let validators = create_validators::<T>(n)?;
 	}: _(RawOrigin::Signed(controller), validators)
+	verify {
+		assert!(Nominators::<T>::contains_key(stash));
+	}
 
 	chill {
 		let u in ...;
@@ -205,61 +270,91 @@ benchmarks! {
 
 	set_payee {
 		let u in ...;
-		let (_, controller) = create_stash_controller::<T>(u)?;
+		let (stash, controller) = create_stash_controller::<T>(u)?;
+		assert_eq!(Payee::<T>::get(&stash), RewardDestination::Staked);
 	}: _(RawOrigin::Signed(controller), RewardDestination::Controller)
+	verify {
+		assert_eq!(Payee::<T>::get(&stash), RewardDestination::Controller);
+	}
 
 	set_controller {
 		let u in ...;
 		let (stash, _) = create_stash_controller::<T>(u)?;
 		let new_controller = create_funded_user::<T>("new_controller", u);
-		let new_controller_lookup = T::Lookup::unlookup(new_controller);
+		let new_controller_lookup = T::Lookup::unlookup(new_controller.clone());
 	}: _(RawOrigin::Signed(stash), new_controller_lookup)
+	verify {
+		assert!(Ledger::<T>::contains_key(&new_controller));
+	}
 
 	set_validator_count {
-		let c in 0 .. 1000;
+		let c in 0 .. MAX_VALIDATORS;
 	}: _(RawOrigin::Root, c)
+	verify {
+		assert_eq!(ValidatorCount::get(), c);
+	}
 
 	force_no_eras { let i in 0 .. 1; }: _(RawOrigin::Root)
+	verify { assert_eq!(ForceEra::get(), Forcing::ForceNone); }
 
 	force_new_era {let i in 0 .. 1; }: _(RawOrigin::Root)
+	verify { assert_eq!(ForceEra::get(), Forcing::ForceNew); }
 
 	force_new_era_always { let i in 0 .. 1; }: _(RawOrigin::Root)
+	verify { assert_eq!(ForceEra::get(), Forcing::ForceAlways); }
 
 	// Worst case scenario, the list of invulnerables is very long.
 	set_invulnerables {
-		let v in 0 .. 1000;
+		let v in 0 .. MAX_VALIDATORS;
 		let mut invulnerables = Vec::new();
 		for i in 0 .. v {
 			invulnerables.push(account("invulnerable", i, SEED));
 		}
 	}: _(RawOrigin::Root, invulnerables)
+	verify {
+		assert_eq!(Invulnerables::<T>::get().len(), v as usize);
+	}
 
 	force_unstake {
-		let u in ...;
-		let (stash, _) = create_stash_controller::<T>(u)?;
-	}: _(RawOrigin::Root, stash)
+		// Slashing Spans
+		let s in 0 .. MAX_SPANS;
+		let (stash, controller) = create_stash_controller::<T>(0)?;
+		add_slashing_spans::<T>(&stash, s);
+	}: _(RawOrigin::Root, stash, s)
+	verify {
+		assert!(!Ledger::<T>::contains_key(&controller));
+	}
 
 	cancel_deferred_slash {
-		let s in 1 .. 1000;
+		let s in 1 .. MAX_SLASHES;
 		let mut unapplied_slashes = Vec::new();
 		let era = EraIndex::one();
-		for _ in 0 .. 1000 {
+		for _ in 0 .. MAX_SLASHES {
 			unapplied_slashes.push(UnappliedSlash::<T::AccountId, BalanceOf<T>>::default());
 		}
 		UnappliedSlashes::<T>::insert(era, &unapplied_slashes);
 
 		let slash_indices: Vec<u32> = (0 .. s).collect();
 	}: _(RawOrigin::Root, era, slash_indices)
+	verify {
+		assert_eq!(UnappliedSlashes::<T>::get(&era).len(), (MAX_SLASHES - s) as usize);
+	}
 
 	payout_stakers {
-		let n in 1 .. MAX_NOMINATIONS as u32;
-		let validator = create_validator_with_nominators::<T>(n, MAX_NOMINATIONS as u32)?;
+		let n in 1 .. T::MaxNominatorRewardedPerValidator::get() as u32;
+		let validator = create_validator_with_nominators::<T>(n, T::MaxNominatorRewardedPerValidator::get() as u32)?;
 		let current_era = CurrentEra::get().unwrap();
-		let caller = account("caller", n, SEED);
-	}: _(RawOrigin::Signed(caller), validator, current_era)
+		let caller = account("caller", 0, SEED);
+		let balance_before = T::Currency::free_balance(&validator);
+	}: _(RawOrigin::Signed(caller), validator.clone(), current_era)
+	verify {
+		// Validator has been paid!
+		let balance_after = T::Currency::free_balance(&validator);
+		assert!(balance_before < balance_after);
+	}
 
 	rebond {
-		let l in 1 .. 1000;
+		let l in 1 .. MAX_UNLOCKING_CHUNKS as u32;
 		let (_, controller) = create_stash_controller::<T>(u)?;
 		let mut staking_ledger = Ledger::<T>::get(controller.clone()).unwrap();
 		let unlock_chunk = UnlockChunk::<BalanceOf<T>> {
@@ -269,8 +364,14 @@ benchmarks! {
 		for _ in 0 .. l {
 			staking_ledger.unlocking.push(unlock_chunk.clone())
 		}
-		Ledger::<T>::insert(controller.clone(), staking_ledger);
-	}: _(RawOrigin::Signed(controller), (l + 100).into())
+		Ledger::<T>::insert(controller.clone(), staking_ledger.clone());
+		let original_bonded: BalanceOf<T> = staking_ledger.active;
+	}: _(RawOrigin::Signed(controller.clone()), (l + 100).into())
+	verify {
+		let ledger = Ledger::<T>::get(&controller).ok_or("ledger not created after")?;
+		let new_bonded: BalanceOf<T> = ledger.active;
+		assert!(original_bonded < new_bonded);
+	}
 
 	set_history_depth {
 		let e in 1 .. 100;
@@ -285,13 +386,20 @@ benchmarks! {
 			<ErasTotalStake<T>>::insert(i, BalanceOf::<T>::one());
 			ErasStartSessionIndex::insert(i, i);
 		}
-	}: _(RawOrigin::Root, EraIndex::zero())
+	}: _(RawOrigin::Root, EraIndex::zero(), u32::max_value())
+	verify {
+		assert_eq!(HistoryDepth::get(), 0);
+	}
 
 	reap_stash {
-		let u in 1 .. 1000;
-		let (stash, controller) = create_stash_controller::<T>(u)?;
+		let s in 1 .. MAX_SPANS;
+		let (stash, controller) = create_stash_controller::<T>(0)?;
+		add_slashing_spans::<T>(&stash, s);
 		T::Currency::make_free_balance_be(&stash, 0.into());
-	}: _(RawOrigin::Signed(controller), stash)
+	}: _(RawOrigin::Signed(controller), stash.clone(), s)
+	verify {
+		assert!(!Bonded::<T>::contains_key(&stash));
+	}
 
 	new_era {
 		let v in 1 .. 10;
@@ -305,7 +413,7 @@ benchmarks! {
 	}
 
 	do_slash {
-		let l in 1 .. 1000;
+		let l in 1 .. MAX_UNLOCKING_CHUNKS as u32;
 		let (stash, controller) = create_stash_controller::<T>(0)?;
 		let mut staking_ledger = Ledger::<T>::get(controller.clone()).unwrap();
 		let unlock_chunk = UnlockChunk::<BalanceOf<T>> {
@@ -317,6 +425,7 @@ benchmarks! {
 		}
 		Ledger::<T>::insert(controller.clone(), staking_ledger.clone());
 		let slash_amount = T::Currency::minimum_balance() * 10.into();
+		let balance_before = T::Currency::free_balance(&stash);
 	}: {
 		crate::slashing::do_slash::<T>(
 			&stash,
@@ -324,6 +433,9 @@ benchmarks! {
 			&mut BalanceOf::<T>::zero(),
 			&mut NegativeImbalanceOf::<T>::zero()
 		);
+	} verify {
+		let balance_after = T::Currency::free_balance(&stash);
+		assert!(balance_before > balance_after);
 	}
 
 	payout_all {
@@ -395,7 +507,7 @@ mod tests {
 
 			let validator_stash = create_validator_with_nominators::<Test>(
 				n,
-				MAX_NOMINATIONS as u32,
+				<Test as Trait>::MaxNominatorRewardedPerValidator::get() as u32,
 			).unwrap();
 
 			let current_era = CurrentEra::get().unwrap();
@@ -408,6 +520,35 @@ mod tests {
 		});
 	}
 
+	#[test]
+	fn add_slashing_spans_works() {
+		ExtBuilder::default().has_stakers(false).build().execute_with(|| {
+			let n = 10;
+
+			let validator_stash = create_validator_with_nominators::<Test>(
+				n,
+				<Test as Trait>::MaxNominatorRewardedPerValidator::get() as u32,
+			).unwrap();
+
+			// Add 20 slashing spans
+			let num_of_slashing_spans = 20;
+			add_slashing_spans::<Test>(&validator_stash, num_of_slashing_spans);
+
+			let slashing_spans = SlashingSpans::<Test>::get(&validator_stash).unwrap();
+			assert_eq!(slashing_spans.iter().count(), num_of_slashing_spans as usize);
+			for i in 0 .. num_of_slashing_spans {
+				assert!(SpanSlash::<Test>::contains_key((&validator_stash, i)));
+			}
+
+			// Test everything is cleaned up
+			assert_ok!(Staking::kill_stash(&validator_stash, num_of_slashing_spans));
+			assert!(SlashingSpans::<Test>::get(&validator_stash).is_none());
+			for i in 0 .. num_of_slashing_spans {
+				assert!(!SpanSlash::<Test>::contains_key((&validator_stash, i)));
+			}
+		});
+	}
+
 	#[test]
 	fn test_payout_all() {
 		ExtBuilder::default().has_stakers(false).build().execute_with(|| {
@@ -432,7 +573,8 @@ mod tests {
 			assert_ok!(test_benchmark_bond::<Test>());
 			assert_ok!(test_benchmark_bond_extra::<Test>());
 			assert_ok!(test_benchmark_unbond::<Test>());
-			assert_ok!(test_benchmark_withdraw_unbonded::<Test>());
+			assert_ok!(test_benchmark_withdraw_unbonded_update::<Test>());
+			assert_ok!(test_benchmark_withdraw_unbonded_kill::<Test>());
 			assert_ok!(test_benchmark_validate::<Test>());
 			assert_ok!(test_benchmark_nominate::<Test>());
 			assert_ok!(test_benchmark_chill::<Test>());
diff --git a/substrate/frame/staking/src/lib.rs b/substrate/frame/staking/src/lib.rs
index 71042d69b3..9d6ff12b1f 100644
--- a/substrate/frame/staking/src/lib.rs
+++ b/substrate/frame/staking/src/lib.rs
@@ -290,9 +290,9 @@ use sp_std::{
 use codec::{HasCompact, Encode, Decode};
 use frame_support::{
 	decl_module, decl_event, decl_storage, ensure, decl_error, debug,
-	weights::{Weight, DispatchClass},
+	weights::{Weight, constants::{WEIGHT_PER_MICROS, WEIGHT_PER_NANOS}},
 	storage::IterableStorageMap,
-	dispatch::{IsSubType, DispatchResult},
+	dispatch::{IsSubType, DispatchResult, DispatchResultWithPostInfo},
 	traits::{
 		Currency, LockIdentifier, LockableCurrency, WithdrawReasons, OnUnbalanced, Imbalance, Get,
 		UnixTime, EstimateNextNewSession, EnsureOrigin,
@@ -1164,6 +1164,10 @@ decl_error! {
 		PhragmenBogusScore,
 		/// The call is not allowed at the given time due to restrictions of election period.
 		CallNotAllowed,
+		/// Incorrect previous history depth input provided.
+		IncorrectHistoryDepth,
+		/// Incorrect number of slashing spans provided.
+		IncorrectSlashingSpans,
 	}
 }
 
@@ -1185,6 +1189,11 @@ decl_module! {
 		/// worker, if applicable, will execute at the end of the current block, and solutions may
 		/// be submitted.
 		fn on_initialize(now: T::BlockNumber) -> Weight {
+			let mut consumed_weight = 0;
+			let mut add_weight = |reads, writes, weight| {
+				consumed_weight += T::DbWeight::get().reads_writes(reads, writes);
+				consumed_weight += weight;
+			};
 			if
 				// if we don't have any ongoing offchain compute.
 				Self::era_election_status().is_closed() &&
@@ -1195,12 +1204,15 @@ decl_module! {
 					if let Some(remaining) = next_session_change.checked_sub(&now) {
 						if remaining <= T::ElectionLookahead::get() && !remaining.is_zero() {
 							// create snapshot.
-							if Self::create_stakers_snapshot() {
+							let (did_snapshot, snapshot_weight) = Self::create_stakers_snapshot();
+							add_weight(0, 0, snapshot_weight);
+							if did_snapshot {
 								// Set the flag to make sure we don't waste any compute here in the same era
 								// after we have triggered the offline compute.
 								<EraElectionStatus<T>>::put(
 									ElectionStatus::<T::BlockNumber>::Open(now)
 								);
+								add_weight(0, 1, 0);
 								log!(info, "💸 Election window is Open({:?}). Snapshot created", now);
 							} else {
 								log!(warn, "💸 Failed to create snapshot at {:?}.", now);
@@ -1210,10 +1222,13 @@ decl_module! {
 				} else {
 					log!(warn, "💸 Estimating next session change failed.");
 				}
+				add_weight(0, 0, T::NextNewSession::weight(now))
 			}
-
-			// weight
-			50_000
+			// For `era_election_status`, `is_current_session_final`, `will_era_be_forced`
+			add_weight(3, 0, 0);
+			// Additional read from `on_finalize`
+			add_weight(1, 0, 0);
+			consumed_weight
 		}
 
 		/// Check if the current block number is the one at which the election window has been set
@@ -1241,9 +1256,11 @@ decl_module! {
 				if active_era.start.is_none() {
 					let now_as_millis_u64 = T::UnixTime::now().as_millis().saturated_into::<u64>();
 					active_era.start = Some(now_as_millis_u64);
+					// This write only ever happens once, we don't include it in the weight in general
 					ActiveEra::put(active_era);
 				}
 			}
+			// `on_finalize` weight is tracked in `on_initialize`
 		}
 
 		/// Take the origin account as a stash and lock up `value` of its balance. `controller` will
@@ -1262,8 +1279,13 @@ decl_module! {
 		///
 		/// NOTE: Two of the storage writes (`Self::bonded`, `Self::payee`) are _never_ cleaned
 		/// unless the `origin` falls below _existential deposit_ and gets removed as dust.
+		/// ------------------
+		/// Base Weight: 67.87 µs
+		/// DB Weight:
+		/// - Read: Bonded, Ledger, [Origin Account], Current Era, History Depth, Locks
+		/// - Write: Bonded, Payee, [Origin Account], Locks, Ledger
 		/// # </weight>
-		#[weight = 500_000_000]
+		#[weight = 67 * WEIGHT_PER_MICROS + T::DbWeight::get().reads_writes(5, 4)]
 		pub fn bond(origin,
 			controller: <T::Lookup as StaticLookup>::Source,
 			#[compact] value: BalanceOf<T>,
@@ -1326,8 +1348,13 @@ decl_module! {
 		/// - Independent of the arguments. Insignificant complexity.
 		/// - O(1).
 		/// - One DB entry.
+		/// ------------
+		/// Base Weight: 54.88 µs
+		/// DB Weight:
+		/// - Read: Era Election Status, Bonded, Ledger, [Origin Account], Locks
+		/// - Write: [Origin Account], Locks, Ledger
 		/// # </weight>
-		#[weight = 500_000_000]
+		#[weight = 55 * WEIGHT_PER_MICROS + T::DbWeight::get().reads_writes(4, 2)]
 		fn bond_extra(origin, #[compact] max_additional: BalanceOf<T>) {
 			ensure!(Self::era_election_status().is_closed(), Error::<T>::CallNotAllowed);
 			let stash = ensure_signed(origin)?;
@@ -1372,8 +1399,13 @@ decl_module! {
 		///   The only way to clean the aforementioned storage item is also user-controlled via
 		///   `withdraw_unbonded`.
 		/// - One DB entry.
+		/// ----------
+		/// Base Weight: 50.34 µs
+		/// DB Weight:
+		/// - Read: Era Election Status, Ledger, Current Era, Locks, [Origin Account]
+		/// - Write: [Origin Account], Locks, Ledger
 		/// </weight>
-		#[weight = 400_000_000]
+		#[weight = 50 * WEIGHT_PER_MICROS + T::DbWeight::get().reads_writes(4, 2)]
 		fn unbond(origin, #[compact] value: BalanceOf<T>) {
 			ensure!(Self::era_election_status().is_closed(), Error::<T>::CallNotAllowed);
 			let controller = ensure_signed(origin)?;
@@ -1420,9 +1452,28 @@ decl_module! {
 		///  indirectly user-controlled. See [`unbond`] for more detail.
 		/// - Contains a limited number of reads, yet the size of which could be large based on `ledger`.
 		/// - Writes are limited to the `origin` account key.
+		/// ---------------
+		/// Complexity O(S) where S is the number of slashing spans to remove
+		/// Base Weight:
+		/// Update: 50.52 + .028 * S µs
+		/// - Reads: EraElectionStatus, Ledger, Current Era, Locks, [Origin Account]
+		/// - Writes: [Origin Account], Locks, Ledger
+		/// Kill: 79.41 + 2.366 * S µs
+		/// - Reads: EraElectionStatus, Ledger, Current Era, Bonded, Slashing Spans, [Origin Account], Locks
+		/// - Writes: Bonded, Slashing Spans (if S > 0), Ledger, Payee, Validators, Nominators, [Origin Account], Locks
+		/// - Writes Each: SpanSlash * S
+		/// NOTE: Weight annotation is the kill scenario, we refund otherwise.
 		/// # </weight>
-		#[weight = 400_000_000]
-		fn withdraw_unbonded(origin) {
+		#[weight = T::DbWeight::get().reads_writes(6, 6)
+			.saturating_add(80 * WEIGHT_PER_MICROS)
+			.saturating_add(
+				(2 * WEIGHT_PER_MICROS).saturating_mul(Weight::from(*num_slashing_spans))
+			)
+			.saturating_add(T::DbWeight::get().writes(Weight::from(*num_slashing_spans)))
+			// if slashing spans is non-zero, add 1 more write
+			.saturating_add(T::DbWeight::get().writes(Weight::from(*num_slashing_spans).min(1)))
+		]
+		fn withdraw_unbonded(origin, num_slashing_spans: u32) -> DispatchResultWithPostInfo {
 			ensure!(Self::era_election_status().is_closed(), Error::<T>::CallNotAllowed);
 			let controller = ensure_signed(origin)?;
 			let mut ledger = Self::ledger(&controller).ok_or(Error::<T>::NotController)?;
@@ -1431,17 +1482,21 @@ decl_module! {
 				ledger = ledger.consolidate_unlocked(current_era)
 			}
 
-			if ledger.unlocking.is_empty() && ledger.active.is_zero() {
+			let post_info_weight = if ledger.unlocking.is_empty() && ledger.active.is_zero() {
 				// This account must have called `unbond()` with some value that caused the active
 				// portion to fall below existential deposit + will have no more unlocking chunks
 				// left. We can now safely remove all staking-related information.
-				Self::kill_stash(&stash)?;
+				Self::kill_stash(&stash, num_slashing_spans)?;
 				// remove the lock.
 				T::Currency::remove_lock(STAKING_ID, &stash);
+				// This is worst case scenario, so we use the full weight and return None
+				None
 			} else {
 				// This was the consequence of a partial unbond. just update the ledger and move on.
 				Self::update_ledger(&controller, &ledger);
-			}
+				// This is only an update, so we use less overall weight
+				Some(50 * WEIGHT_PER_MICROS + T::DbWeight::get().reads_writes(4, 2))
+			};
 
 			// `old_total` should never be less than the new total because
 			// `consolidate_unlocked` strictly subtracts balance.
@@ -1450,6 +1505,8 @@ decl_module! {
 				let value = old_total - ledger.total;
 				Self::deposit_event(RawEvent::Withdrawn(stash, value));
 			}
+
+			Ok(post_info_weight.into())
 		}
 
 		/// Declare the desire to validate for the origin controller.
@@ -1463,8 +1520,13 @@ decl_module! {
 		/// - Independent of the arguments. Insignificant complexity.
 		/// - Contains a limited number of reads.
 		/// - Writes are limited to the `origin` account key.
+		/// -----------
+		/// Base Weight: 17.13 µs
+		/// DB Weight:
+		/// - Read: Era Election Status, Ledger
+		/// - Write: Nominators, Validators
 		/// # </weight>
-		#[weight = 750_000_000]
+		#[weight = 17 * WEIGHT_PER_MICROS + T::DbWeight::get().reads_writes(2, 2)]
 		pub fn validate(origin, prefs: ValidatorPrefs) {
 			ensure!(Self::era_election_status().is_closed(), Error::<T>::CallNotAllowed);
 			let controller = ensure_signed(origin)?;
@@ -1483,11 +1545,20 @@ decl_module! {
 		/// And, it can be only called when [`EraElectionStatus`] is `Closed`.
 		///
 		/// # <weight>
-		/// - The transaction's complexity is proportional to the size of `targets`,
-		/// which is capped at CompactAssignments::LIMIT.
+		/// - The transaction's complexity is proportional to the size of `targets` (N)
+		/// which is capped at CompactAssignments::LIMIT (MAX_NOMINATIONS).
 		/// - Both the reads and writes follow a similar pattern.
+		/// ---------
+		/// Base Weight: 22.34 + .36 * N µs
+		/// where N is the number of targets
+		/// DB Weight:
+		/// - Reads: Era Election Status, Ledger, Current Era
+		/// - Writes: Validators, Nominators
 		/// # </weight>
-		#[weight = 750_000_000]
+		#[weight = T::DbWeight::get().reads_writes(3, 2)
+			.saturating_add(22 * WEIGHT_PER_MICROS)
+			.saturating_add((360 * WEIGHT_PER_NANOS).saturating_mul(targets.len() as Weight))
+		]
 		pub fn nominate(origin, targets: Vec<<T::Lookup as StaticLookup>::Source>) {
 			ensure!(Self::era_election_status().is_closed(), Error::<T>::CallNotAllowed);
 			let controller = ensure_signed(origin)?;
@@ -1495,7 +1566,7 @@ decl_module! {
 			let stash = &ledger.stash;
 			ensure!(!targets.is_empty(), Error::<T>::EmptyTargets);
 			let targets = targets.into_iter()
-				.take(<CompactAssignments as VotingLimit>::LIMIT)
+				.take(MAX_NOMINATIONS)
 				.map(|t| T::Lookup::lookup(t))
 				.collect::<result::Result<Vec<T::AccountId>, _>>()?;
 
@@ -1521,8 +1592,13 @@ decl_module! {
 		/// - Independent of the arguments. Insignificant complexity.
 		/// - Contains one read.
 		/// - Writes are limited to the `origin` account key.
+		/// --------
+		/// Base Weight: 16.53 µs
+		/// DB Weight:
+		/// - Read: EraElectionStatus, Ledger
+		/// - Write: Validators, Nominators
 		/// # </weight>
-		#[weight = 500_000_000]
+		#[weight = 16 * WEIGHT_PER_MICROS + T::DbWeight::get().reads_writes(2, 2)]
 		fn chill(origin) {
 			ensure!(Self::era_election_status().is_closed(), Error::<T>::CallNotAllowed);
 			let controller = ensure_signed(origin)?;
@@ -1540,8 +1616,13 @@ decl_module! {
 		/// - Independent of the arguments. Insignificant complexity.
 		/// - Contains a limited number of reads.
 		/// - Writes are limited to the `origin` account key.
+		/// ---------
+		/// - Base Weight: 11.33 µs
+		/// - DB Weight:
+		///     - Read: Ledger
+		///     - Write: Payee
 		/// # </weight>
-		#[weight = 500_000_000]
+		#[weight = 11 * WEIGHT_PER_MICROS + T::DbWeight::get().reads_writes(1, 1)]
 		fn set_payee(origin, payee: RewardDestination) {
 			let controller = ensure_signed(origin)?;
 			let ledger = Self::ledger(&controller).ok_or(Error::<T>::NotController)?;
@@ -1559,8 +1640,13 @@ decl_module! {
 		/// - Independent of the arguments. Insignificant complexity.
 		/// - Contains a limited number of reads.
 		/// - Writes are limited to the `origin` account key.
+		/// ----------
+		/// Base Weight: 25.22 µs
+		/// DB Weight:
+		/// - Read: Bonded, Ledger New Controller, Ledger Old Controller
+		/// - Write: Bonded, Ledger New Controller, Ledger Old Controller
 		/// # </weight>
-		#[weight = 750_000_000]
+		#[weight = 25 * WEIGHT_PER_MICROS + T::DbWeight::get().reads_writes(3, 3)]
 		fn set_controller(origin, controller: <T::Lookup as StaticLookup>::Source) {
 			let stash = ensure_signed(origin)?;
 			let old_controller = Self::bonded(&stash).ok_or(Error::<T>::NotStash)?;
@@ -1576,8 +1662,15 @@ decl_module! {
 			}
 		}
 
-		/// The ideal number of validators.
-		#[weight = 5_000_000]
+		/// Sets the ideal number of validators.
+		///
+		/// The dispatch origin must be Root.
+		///
+		/// # <weight>
+		/// Base Weight: 1.717 µs
+		/// Write: Validator Count
+		/// # </weight>
+		#[weight = 2 * WEIGHT_PER_MICROS + T::DbWeight::get().writes(1)]
 		fn set_validator_count(origin, #[compact] new: u32) {
 			ensure_root(origin)?;
 			ValidatorCount::put(new);
@@ -1585,10 +1678,14 @@ decl_module! {
 
 		/// Force there to be no new eras indefinitely.
 		///
+		/// The dispatch origin must be Root.
+		///
 		/// # <weight>
 		/// - No arguments.
+		/// - Base Weight: 1.857 µs
+		/// - Write: ForceEra
 		/// # </weight>
-		#[weight = 5_000_000]
+		#[weight = 2 * WEIGHT_PER_MICROS + T::DbWeight::get().writes(1)]
 		fn force_no_eras(origin) {
 			ensure_root(origin)?;
 			ForceEra::put(Forcing::ForceNone);
@@ -1597,29 +1694,62 @@ decl_module! {
 		/// Force there to be a new era at the end of the next session. After this, it will be
 		/// reset to normal (non-forced) behaviour.
 		///
+		/// The dispatch origin must be Root.
+		///
 		/// # <weight>
 		/// - No arguments.
+		/// - Base Weight: 1.959 µs
+		/// - Write ForceEra
 		/// # </weight>
-		#[weight = 5_000_000]
+		#[weight = 2 * WEIGHT_PER_MICROS + T::DbWeight::get().writes(1)]
 		fn force_new_era(origin) {
 			ensure_root(origin)?;
 			ForceEra::put(Forcing::ForceNew);
 		}
 
 		/// Set the validators who cannot be slashed (if any).
-		#[weight = 5_000_000]
+		///
+		/// The dispatch origin must be Root.
+		///
+		/// # <weight>
+		/// - O(V)
+		/// - Base Weight: 2.208 + .006 * V µs
+		/// - Write: Invulnerables
+		/// # </weight>
+		#[weight = T::DbWeight::get().writes(1)
+			.saturating_add(2 * WEIGHT_PER_MICROS)
+			.saturating_add((6 * WEIGHT_PER_NANOS).saturating_mul(validators.len() as Weight))
+		]
 		fn set_invulnerables(origin, validators: Vec<T::AccountId>) {
 			ensure_root(origin)?;
 			<Invulnerables<T>>::put(validators);
 		}
 
 		/// Force a current staker to become completely unstaked, immediately.
-		#[weight = 0]
-		fn force_unstake(origin, stash: T::AccountId) {
+		///
+		/// The dispatch origin must be Root.
+		///
+		/// # <weight>
+		/// O(S) where S is the number of slashing spans to be removed
+		/// Base Weight: 53.07 + 2.365 * S µs
+		/// Reads: Bonded, Slashing Spans, Account, Locks
+		/// Writes: Bonded, Slashing Spans (if S > 0), Ledger, Payee, Validators, Nominators, Account, Locks
+		/// Writes Each: SpanSlash * S
+		/// # </weight>
+		#[weight = T::DbWeight::get().reads_writes(4, 7)
+			.saturating_add(53 * WEIGHT_PER_MICROS)
+			.saturating_add(
+				WEIGHT_PER_MICROS.saturating_mul(2).saturating_mul(Weight::from(*num_slashing_spans))
+			)
+			.saturating_add(T::DbWeight::get().writes(Weight::from(*num_slashing_spans)))
+			// if slashing spans is non-zero, add 1 more write
+			.saturating_add(T::DbWeight::get().writes(Weight::from(*num_slashing_spans > 0)))
+		]
+		fn force_unstake(origin, stash: T::AccountId, num_slashing_spans: u32) {
 			ensure_root(origin)?;
 
 			// remove all staking-related information.
-			Self::kill_stash(&stash)?;
+			Self::kill_stash(&stash, num_slashing_spans)?;
 
 			// remove the lock.
 			T::Currency::remove_lock(STAKING_ID, &stash);
@@ -1627,23 +1757,36 @@ decl_module! {
 
 		/// Force there to be a new era at the end of sessions indefinitely.
 		///
+		/// The dispatch origin must be Root.
+		///
 		/// # <weight>
-		/// - One storage write
+		/// - Base Weight: 2.05 µs
+		/// - Write: ForceEra
 		/// # </weight>
-		#[weight = 5_000_000]
+		#[weight = 2 * WEIGHT_PER_MICROS + T::DbWeight::get().writes(1)]
 		fn force_new_era_always(origin) {
 			ensure_root(origin)?;
 			ForceEra::put(Forcing::ForceAlways);
 		}
 
-		/// Cancel enactment of a deferred slash. Can be called by either the root origin or
-		/// the `T::SlashCancelOrigin`.
-		/// passing the era and indices of the slashes for that era to kill.
+		/// Cancel enactment of a deferred slash.
+		///
+		/// Can be called by either the root origin or the `T::SlashCancelOrigin`.
+		///
+		/// Parameters: era and indices of the slashes for that era to kill.
 		///
 		/// # <weight>
-		/// - One storage write.
+		/// Complexity: O(U + S)
+		/// with U unapplied slashes weighted with U=1000
+		/// and S is the number of slash indices to be canceled.
+		/// - Base: 5870 + 34.61 * S µs
+		/// - Read: Unapplied Slashes
+		/// - Write: Unapplied Slashes
 		/// # </weight>
-		#[weight = 1_000_000_000]
+		#[weight = T::DbWeight::get().reads_writes(1, 1)
+			.saturating_add(5_870 * WEIGHT_PER_MICROS)
+			.saturating_add((35 * WEIGHT_PER_MICROS).saturating_mul(slash_indices.len() as Weight))
+		]
 		fn cancel_deferred_slash(origin, era: EraIndex, slash_indices: Vec<u32>) {
 			T::SlashCancelOrigin::try_origin(origin)
 				.map(|_| ())
@@ -1741,8 +1884,23 @@ decl_module! {
 		/// # <weight>
 		/// - Time complexity: at most O(MaxNominatorRewardedPerValidator).
 		/// - Contains a limited number of reads and writes.
+		/// -----------
+		/// N is the Number of payouts for the validator (including the validator)
+		/// Base Weight: 110 + 54.2 * N µs (Median Slopes)
+		/// DB Weight:
+		/// - Read: EraElectionStatus, CurrentEra, HistoryDepth, MigrateEra, ErasValidatorReward,
+		///         ErasStakersClipped, ErasRewardPoints, ErasValidatorPrefs (8 items)
+		/// - Read Each: Bonded, Ledger, Payee, Locks, System Account (5 items)
+		/// - Write Each: System Account, Locks, Ledger (3 items)
+		// TODO: Remove read on Migrate Era
 		/// # </weight>
-		#[weight = 500_000_000]
+		#[weight =
+			110 * WEIGHT_PER_MICROS
+			+ 54 * WEIGHT_PER_MICROS * Weight::from(T::MaxNominatorRewardedPerValidator::get())
+			+ T::DbWeight::get().reads(8)
+			+ T::DbWeight::get().reads(5)  * Weight::from(T::MaxNominatorRewardedPerValidator::get() + 1)
+			+ T::DbWeight::get().writes(3) * Weight::from(T::MaxNominatorRewardedPerValidator::get() + 1)
+		]
 		fn payout_stakers(origin, validator_stash: T::AccountId, era: EraIndex) -> DispatchResult {
 			ensure!(Self::era_election_status().is_closed(), Error::<T>::CallNotAllowed);
 			ensure_signed(origin)?;
@@ -1755,11 +1913,21 @@ decl_module! {
 		/// [`EraElectionStatus`] is `Closed`.
 		///
 		/// # <weight>
-		/// - Time complexity: O(1). Bounded by `MAX_UNLOCKING_CHUNKS`.
+		/// - Time complexity: O(L), where L is unlocking chunks
+		/// - Bounded by `MAX_UNLOCKING_CHUNKS`.
 		/// - Storage changes: Can't increase storage, only decrease it.
+		/// ---------------
+		/// - Base Weight: 34.51 µs * .048 L µs
+		/// - DB Weight:
+		///     - Reads: EraElectionStatus, Ledger, Locks, [Origin Account]
+		///     - Writes: [Origin Account], Locks, Ledger
 		/// # </weight>
-		#[weight = 500_000_000]
-		fn rebond(origin, #[compact] value: BalanceOf<T>) {
+		#[weight =
+			35 * WEIGHT_PER_MICROS
+			+ 50 * WEIGHT_PER_NANOS * (MAX_UNLOCKING_CHUNKS as Weight)
+			+ T::DbWeight::get().reads_writes(3, 2)
+		]
+		fn rebond(origin, #[compact] value: BalanceOf<T>) -> DispatchResultWithPostInfo {
 			ensure!(Self::era_election_status().is_closed(), Error::<T>::CallNotAllowed);
 			let controller = ensure_signed(origin)?;
 			let ledger = Self::ledger(&controller).ok_or(Error::<T>::NotController)?;
@@ -1767,13 +1935,44 @@ decl_module! {
 
 			let ledger = ledger.rebond(value);
 			Self::update_ledger(&controller, &ledger);
+			Ok(Some(
+				35 * WEIGHT_PER_MICROS
+				+ 50 * WEIGHT_PER_NANOS * (ledger.unlocking.len() as Weight)
+				+ T::DbWeight::get().reads_writes(3, 2)
+			).into())
 		}
 
-		/// Set history_depth value.
+		/// Set `HistoryDepth` value. This function will delete any history information
+		/// when `HistoryDepth` is reduced.
+		///
+		/// Parameters:
+		/// - `new_history_depth`: The new history depth you would like to set.
+		/// - `era_items_deleted`: The number of items that will be deleted by this dispatch.
+		///    This should report all the storage items that will be deleted by clearing old
+		///    era history. Needed to report an accurate weight for the dispatch. Trusted by
+		///    `Root` to report an accurate number.
 		///
 		/// Origin must be root.
-		#[weight = (500_000_000, DispatchClass::Operational)]
-		fn set_history_depth(origin, #[compact] new_history_depth: EraIndex) {
+		///
+		/// # <weight>
+		/// - E: Number of history depths removed, i.e. 10 -> 7 = 3
+		/// - Base Weight: 29.13 * E µs
+		/// - DB Weight:
+		///     - Reads: Current Era, History Depth
+		///     - Writes: History Depth
+		///     - Clear Prefix Each: Era Stakers, EraStakersClipped, ErasValidatorPrefs
+		///     - Writes Each: ErasValidatorReward, ErasRewardPoints, ErasTotalStake, ErasStartSessionIndex
+		/// # </weight>
+		#[weight = {
+			let items = Weight::from(*_era_items_deleted);
+			T::DbWeight::get().reads_writes(2, 1)
+				.saturating_add(T::DbWeight::get().reads_writes(items, items))
+
+		}]
+		fn set_history_depth(origin,
+			#[compact] new_history_depth: EraIndex,
+			#[compact] _era_items_deleted: u32,
+		) {
 			ensure_root(origin)?;
 			if let Some(current_era) = Self::current_era() {
 				HistoryDepth::mutate(|history_depth| {
@@ -1794,10 +1993,27 @@ decl_module! {
 		/// This can be called from any origin.
 		///
 		/// - `stash`: The stash account to reap. Its balance must be zero.
-		#[weight = 0]
-		fn reap_stash(_origin, stash: T::AccountId) {
+		///
+		/// # <weight>
+		/// Complexity: O(S) where S is the number of slashing spans on the account.
+		/// Base Weight: 75.94 + 2.396 * S µs
+		/// DB Weight:
+		/// - Reads: Stash Account, Bonded, Slashing Spans, Locks
+		/// - Writes: Bonded, Slashing Spans (if S > 0), Ledger, Payee, Validators, Nominators, Stash Account, Locks
+		/// - Writes Each: SpanSlash * S
+		/// # </weight>
+		#[weight = T::DbWeight::get().reads_writes(4, 7)
+			.saturating_add(76 * WEIGHT_PER_MICROS)
+			.saturating_add(
+				WEIGHT_PER_MICROS.saturating_mul(2).saturating_mul(Weight::from(*num_slashing_spans))
+			)
+			.saturating_add(T::DbWeight::get().writes(Weight::from(*num_slashing_spans)))
+			// if slashing spans is non-zero, add 1 more write
+			.saturating_add(T::DbWeight::get().writes(Weight::from(*num_slashing_spans).min(1)))
+		]
+		fn reap_stash(_origin, stash: T::AccountId, num_slashing_spans: u32) {
 			ensure!(T::Currency::total_balance(&stash).is_zero(), Error::<T>::FundedTarget);
-			Self::kill_stash(&stash)?;
+			Self::kill_stash(&stash, num_slashing_spans)?;
 			T::Currency::remove_lock(STAKING_ID, &stash);
 		}
 
@@ -1939,12 +2155,18 @@ impl<T: Trait> Module<T> {
 	///
 	/// This data is used to efficiently evaluate election results. returns `true` if the operation
 	/// is successful.
-	fn create_stakers_snapshot() -> bool {
+	fn create_stakers_snapshot() -> (bool, Weight) {
+		let mut consumed_weight = 0;
+		let mut add_db_reads_writes = |reads, writes| {
+			consumed_weight += T::DbWeight::get().reads_writes(reads, writes);
+		};
 		let validators = <Validators<T>>::iter().map(|(v, _)| v).collect::<Vec<_>>();
 		let mut nominators = <Nominators<T>>::iter().map(|(n, _)| n).collect::<Vec<_>>();
 
 		let num_validators = validators.len();
 		let num_nominators = nominators.len();
+		add_db_reads_writes((num_validators + num_nominators) as Weight, 0);
+
 		if
 			num_validators > MAX_VALIDATORS ||
 			num_nominators.saturating_add(num_validators) > MAX_NOMINATORS
@@ -1957,14 +2179,15 @@ impl<T: Trait> Module<T> {
 				num_nominators,
 				MAX_NOMINATORS,
 			);
-			false
+			(false, consumed_weight)
 		} else {
 			// all validators nominate themselves;
 			nominators.extend(validators.clone());
 
 			<SnapshotValidators<T>>::put(validators);
 			<SnapshotNominators<T>>::put(nominators);
-			true
+			add_db_reads_writes(0, 2);
+			(true, consumed_weight)
 		}
 	}
 
@@ -2804,16 +3027,18 @@ impl<T: Trait> Module<T> {
 	/// This is called:
 	/// - after a `withdraw_unbond()` call that frees all of a stash's bonded balance.
 	/// - through `reap_stash()` if the balance has fallen to zero (through slashing).
-	fn kill_stash(stash: &T::AccountId) -> DispatchResult {
-		let controller = Bonded::<T>::take(stash).ok_or(Error::<T>::NotStash)?;
+	fn kill_stash(stash: &T::AccountId, num_slashing_spans: u32) -> DispatchResult {
+		let controller = Bonded::<T>::get(stash).ok_or(Error::<T>::NotStash)?;
+
+		slashing::clear_stash_metadata::<T>(stash, num_slashing_spans)?;
+
+		Bonded::<T>::remove(stash);
 		<Ledger<T>>::remove(&controller);
 
 		<Payee<T>>::remove(stash);
 		<Validators<T>>::remove(stash);
 		<Nominators<T>>::remove(stash);
 
-		slashing::clear_stash_metadata::<T>(stash);
-
 		system::Module::<T>::dec_ref(stash);
 
 		Ok(())
diff --git a/substrate/frame/staking/src/mock.rs b/substrate/frame/staking/src/mock.rs
index b09d026eb3..9c908f6145 100644
--- a/substrate/frame/staking/src/mock.rs
+++ b/substrate/frame/staking/src/mock.rs
@@ -27,7 +27,7 @@ use frame_support::{
 	assert_ok, impl_outer_origin, parameter_types, impl_outer_dispatch, impl_outer_event,
 	StorageValue, StorageMap, StorageDoubleMap, IterableStorageMap,
 	traits::{Currency, Get, FindAuthor, OnFinalize, OnInitialize},
-	weights::Weight,
+	weights::{Weight, constants::RocksDbWeight},
 };
 use sp_io;
 use sp_phragmen::{
@@ -36,7 +36,7 @@ use sp_phragmen::{
 };
 use crate::*;
 
-const INIT_TIMESTAMP: u64 = 30_000;
+pub const INIT_TIMESTAMP: u64 = 30_000;
 
 /// The AccountId alias in this test module.
 pub(crate) type AccountId = u64;
@@ -211,7 +211,7 @@ impl frame_system::Trait for Test {
 	type Event = MetaEvent;
 	type BlockHashCount = BlockHashCount;
 	type MaximumBlockWeight = MaximumBlockWeight;
-	type DbWeight = ();
+	type DbWeight = RocksDbWeight;
 	type BlockExecutionWeight = ();
 	type ExtrinsicBaseWeight = ();
 	type AvailableBlockRatio = AvailableBlockRatio;
@@ -763,6 +763,18 @@ pub(crate) fn on_offence_now(
 	on_offence_in_era(offenders, slash_fraction, now)
 }
 
+pub(crate) fn add_slash(who: &AccountId) {
+	on_offence_now(
+		&[
+			OffenceDetails {
+				offender: (who.clone(), Staking::eras_stakers(Staking::active_era().unwrap().index, who.clone())),
+				reporters: vec![],
+			},
+		],
+		&[Perbill::from_percent(10)],
+	);
+}
+
 // winners will be chosen by simply their unweighted total backing stake. Nominator stake is
 // distributed evenly.
 pub(crate) fn horrible_phragmen_with_post_processing(
diff --git a/substrate/frame/staking/src/slashing.rs b/substrate/frame/staking/src/slashing.rs
index 26f0828989..7dccf24cb2 100644
--- a/substrate/frame/staking/src/slashing.rs
+++ b/substrate/frame/staking/src/slashing.rs
@@ -50,11 +50,11 @@
 
 use super::{
 	EraIndex, Trait, Module, Store, BalanceOf, Exposure, Perbill, SessionInterface,
-	NegativeImbalanceOf, UnappliedSlash,
+	NegativeImbalanceOf, UnappliedSlash, Error,
 };
-use sp_runtime::{traits::{Zero, Saturating}, RuntimeDebug};
+use sp_runtime::{traits::{Zero, Saturating}, RuntimeDebug, DispatchResult};
 use frame_support::{
-	StorageMap, StorageDoubleMap,
+	StorageMap, StorageDoubleMap, ensure,
 	traits::{Currency, OnUnbalanced, Imbalance},
 };
 use sp_std::vec::Vec;
@@ -100,7 +100,7 @@ pub struct SlashingSpans {
 impl SlashingSpans {
 	// creates a new record of slashing spans for a stash, starting at the beginning
 	// of the bonding period, relative to now.
-	fn new(window_start: EraIndex) -> Self {
+	pub(crate) fn new(window_start: EraIndex) -> Self {
 		SlashingSpans {
 			span_index: 0,
 			last_start: window_start,
@@ -115,7 +115,7 @@ impl SlashingSpans {
 	// update the slashing spans to reflect the start of a new span at the era after `now`
 	// returns `true` if a new span was started, `false` otherwise. `false` indicates
 	// that internal state is unchanged.
-	fn end_span(&mut self, now: EraIndex) -> bool {
+	pub(crate) fn end_span(&mut self, now: EraIndex) -> bool {
 		let next_start = now + 1;
 		if next_start <= self.last_start { return false }
 
@@ -547,12 +547,19 @@ pub(crate) fn clear_era_metadata<T: Trait>(obsolete_era: EraIndex) {
 }
 
 /// Clear slashing metadata for a dead account.
-pub(crate) fn clear_stash_metadata<T: Trait>(stash: &T::AccountId) {
-	let spans = match <Module<T> as Store>::SlashingSpans::take(stash) {
-		None => return,
+pub(crate) fn clear_stash_metadata<T: Trait>(
+	stash: &T::AccountId,
+	num_slashing_spans: u32,
+) -> DispatchResult {
+	let spans = match <Module<T> as Store>::SlashingSpans::get(stash) {
+		None => return Ok(()),
 		Some(s) => s,
 	};
 
+	ensure!(num_slashing_spans as usize >= spans.iter().count(), Error::<T>::IncorrectSlashingSpans);
+
+	<Module<T> as Store>::SlashingSpans::remove(stash);
+
 	// kill slashing-span metadata for account.
 	//
 	// this can only happen while the account is staked _if_ they are completely slashed.
@@ -561,6 +568,8 @@ pub(crate) fn clear_stash_metadata<T: Trait>(stash: &T::AccountId) {
 	for span in spans.iter() {
 		<Module<T> as Store>::SpanSlash::remove(&(stash.clone(), span.index));
 	}
+
+	Ok(())
 }
 
 // apply the slash to a stash account, deducting any missing funds from the reward
diff --git a/substrate/frame/staking/src/tests.rs b/substrate/frame/staking/src/tests.rs
index 9cda151b70..637f8a32dd 100644
--- a/substrate/frame/staking/src/tests.rs
+++ b/substrate/frame/staking/src/tests.rs
@@ -24,7 +24,7 @@ use sp_runtime::{
 use sp_staking::offence::OffenceDetails;
 use frame_support::{
 	assert_ok, assert_noop, StorageMap,
-	traits::{Currency, ReservableCurrency, OnInitialize},
+	traits::{Currency, ReservableCurrency, OnInitialize, OnFinalize},
 };
 use pallet_balances::Error as BalancesError;
 use substrate_test_utils::assert_eq_uvec;
@@ -34,15 +34,19 @@ fn force_unstake_works() {
 	ExtBuilder::default().build_and_execute(|| {
 		// Account 11 is stashed and locked, and account 10 is the controller
 		assert_eq!(Staking::bonded(&11), Some(10));
+		// Adds 2 slashing spans
+		add_slash(&11);
 		// Cant transfer
 		assert_noop!(
 			Balances::transfer(Origin::signed(11), 1, 10),
 			BalancesError::<Test, _>::LiquidityRestrictions
 		);
 		// Force unstake requires root.
-		assert_noop!(Staking::force_unstake(Origin::signed(11), 11), BadOrigin);
+		assert_noop!(Staking::force_unstake(Origin::signed(11), 11, 2), BadOrigin);
+		// Force unstake needs correct number of slashing spans (for weight calculation)
+		assert_noop!(Staking::force_unstake(Origin::signed(11), 11, 0), BadOrigin);
 		// We now force them to unstake
-		assert_ok!(Staking::force_unstake(Origin::ROOT, 11));
+		assert_ok!(Staking::force_unstake(Origin::ROOT, 11, 2));
 		// No longer bonded.
 		assert_eq!(Staking::bonded(&11), None);
 		// Transfer works.
@@ -50,6 +54,24 @@ fn force_unstake_works() {
 	});
 }
 
+#[test]
+fn kill_stash_works() {
+	ExtBuilder::default().build_and_execute(|| {
+		// Account 11 is stashed and locked, and account 10 is the controller
+		assert_eq!(Staking::bonded(&11), Some(10));
+		// Adds 2 slashing spans
+		add_slash(&11);
+		// Only can kill a stash account
+		assert_noop!(Staking::kill_stash(&12, 0), Error::<Test>::NotStash);
+		// Respects slashing span count
+		assert_noop!(Staking::kill_stash(&11, 0), Error::<Test>::IncorrectSlashingSpans);
+		// Correct inputs, everything works
+		assert_ok!(Staking::kill_stash(&11, 2));
+		// No longer bonded.
+		assert_eq!(Staking::bonded(&11), None);
+	});
+}
+
 #[test]
 fn basic_setup_works() {
 	// Verifies initial conditions of mock
@@ -1023,7 +1045,10 @@ fn bond_extra_and_withdraw_unbonded_works() {
 			unlocking: vec![],
 			claimed_rewards: vec![],
 		}));
-		assert_eq!(Staking::eras_stakers(Staking::active_era().unwrap().index, 11), Exposure { total: 1000, own: 1000, others: vec![] });
+		assert_eq!(
+			Staking::eras_stakers(Staking::active_era().unwrap().index, 11),
+			Exposure { total: 1000, own: 1000, others: vec![] }
+		);
 
 		// deposit the extra 100 units
 		Staking::bond_extra(Origin::signed(11), 100).unwrap();
@@ -1036,7 +1061,10 @@ fn bond_extra_and_withdraw_unbonded_works() {
 			claimed_rewards: vec![],
 		}));
 		// Exposure is a snapshot! only updated after the next era update.
-		assert_ne!(Staking::eras_stakers(Staking::active_era().unwrap().index, 11), Exposure { total: 1000 + 100, own: 1000 + 100, others: vec![] });
+		assert_ne!(
+			Staking::eras_stakers(Staking::active_era().unwrap().index, 11),
+			Exposure { total: 1000 + 100, own: 1000 + 100, others: vec![] }
+		);
 
 		// trigger next era.
 		mock::start_era(2);
@@ -1051,34 +1079,68 @@ fn bond_extra_and_withdraw_unbonded_works() {
 			claimed_rewards: vec![],
 		}));
 		// Exposure is now updated.
-		assert_eq!(Staking::eras_stakers(Staking::active_era().unwrap().index, 11), Exposure { total: 1000 + 100, own: 1000 + 100, others: vec![] });
+		assert_eq!(
+			Staking::eras_stakers(Staking::active_era().unwrap().index, 11),
+			Exposure { total: 1000 + 100, own: 1000 + 100, others: vec![] }
+		);
 
 		// Unbond almost all of the funds in stash.
 		Staking::unbond(Origin::signed(10), 1000).unwrap();
-		assert_eq!(Staking::ledger(&10), Some(StakingLedger {
-			stash: 11, total: 1000 + 100, active: 100, unlocking: vec![UnlockChunk{ value: 1000, era: 2 + 3}], claimed_rewards: vec![] })
+		assert_eq!(
+			Staking::ledger(&10),
+			Some(StakingLedger {
+				stash: 11,
+				total: 1000 + 100,
+				active: 100,
+				unlocking: vec![UnlockChunk{ value: 1000, era: 2 + 3}],
+				claimed_rewards: vec![]
+			}),
 		);
 
 		// Attempting to free the balances now will fail. 2 eras need to pass.
-		Staking::withdraw_unbonded(Origin::signed(10)).unwrap();
-		assert_eq!(Staking::ledger(&10), Some(StakingLedger {
-			stash: 11, total: 1000 + 100, active: 100, unlocking: vec![UnlockChunk{ value: 1000, era: 2 + 3}], claimed_rewards: vec![] }));
+		assert_ok!(Staking::withdraw_unbonded(Origin::signed(10), 0));
+		assert_eq!(
+			Staking::ledger(&10),
+			Some(StakingLedger {
+				stash: 11,
+				total: 1000 + 100,
+				active: 100,
+				unlocking: vec![UnlockChunk{ value: 1000, era: 2 + 3}],
+				claimed_rewards: vec![]
+			}),
+		);
 
 		// trigger next era.
 		mock::start_era(3);
 
 		// nothing yet
-		Staking::withdraw_unbonded(Origin::signed(10)).unwrap();
-		assert_eq!(Staking::ledger(&10), Some(StakingLedger {
-			stash: 11, total: 1000 + 100, active: 100, unlocking: vec![UnlockChunk{ value: 1000, era: 2 + 3}], claimed_rewards: vec![] }));
+		assert_ok!(Staking::withdraw_unbonded(Origin::signed(10), 0));
+		assert_eq!(
+			Staking::ledger(&10),
+			Some(StakingLedger {
+				stash: 11,
+				total: 1000 + 100,
+				active: 100,
+				unlocking: vec![UnlockChunk{ value: 1000, era: 2 + 3}],
+				claimed_rewards: vec![]
+			}),
+		);
 
 		// trigger next era.
 		mock::start_era(5);
 
-		Staking::withdraw_unbonded(Origin::signed(10)).unwrap();
+		assert_ok!(Staking::withdraw_unbonded(Origin::signed(10), 0));
 		// Now the value is free and the staking ledger is updated.
-		assert_eq!(Staking::ledger(&10), Some(StakingLedger {
-			stash: 11, total: 100, active: 100, unlocking: vec![], claimed_rewards: vec![] }));
+		assert_eq!(
+			Staking::ledger(&10),
+			Some(StakingLedger {
+				stash: 11,
+				total: 100,
+				active: 100,
+				unlocking: vec![],
+				claimed_rewards: vec![]
+			}),
+		);
 	})
 }
 
@@ -1101,7 +1163,7 @@ fn too_many_unbond_calls_should_not_work() {
 
 		assert_noop!(Staking::unbond(Origin::signed(10), 1), Error::<Test>::NoMoreChunks);
 		// free up.
-		assert_ok!(Staking::withdraw_unbonded(Origin::signed(10)));
+		assert_ok!(Staking::withdraw_unbonded(Origin::signed(10), 0));
 
 		// Can add again.
 		assert_ok!(Staking::unbond(Origin::signed(10), 1));
@@ -1449,7 +1511,7 @@ fn on_free_balance_zero_stash_removes_validator() {
 		assert_eq!(Balances::total_balance(&11), 0);
 
 		// Reap the stash
-		assert_ok!(Staking::reap_stash(Origin::NONE, 11));
+		assert_ok!(Staking::reap_stash(Origin::NONE, 11, 0));
 
 		// Check storage items do not exist
 		assert!(!<Ledger<Test>>::contains_key(&10));
@@ -1505,7 +1567,7 @@ fn on_free_balance_zero_stash_removes_nominator() {
 		assert_eq!(Balances::total_balance(&11), 0);
 
 		// Reap the stash
-		assert_ok!(Staking::reap_stash(Origin::NONE, 11));
+		assert_ok!(Staking::reap_stash(Origin::NONE, 11, 0));
 
 		// Check storage items do not exist
 		assert!(!<Ledger<Test>>::contains_key(&10));
@@ -1619,14 +1681,14 @@ fn bond_with_no_staked_value() {
 			mock::start_era(2);
 
 			// not yet removed.
-			assert_ok!(Staking::withdraw_unbonded(Origin::signed(2)));
+			assert_ok!(Staking::withdraw_unbonded(Origin::signed(2), 0));
 			assert!(Staking::ledger(2).is_some());
 			assert_eq!(Balances::locks(&1)[0].amount, 5);
 
 			mock::start_era(3);
 
 			// poof. Account 1 is removed from the staking system.
-			assert_ok!(Staking::withdraw_unbonded(Origin::signed(2)));
+			assert_ok!(Staking::withdraw_unbonded(Origin::signed(2), 0));
 			assert!(Staking::ledger(2).is_none());
 			assert_eq!(Balances::locks(&1).len(), 0);
 		});
@@ -2270,7 +2332,12 @@ fn garbage_collection_after_slashing() {
 		assert_eq!(Balances::free_balance(11), 0);
 		assert_eq!(Balances::total_balance(&11), 0);
 
-		assert_ok!(Staking::reap_stash(Origin::NONE, 11));
+		let slashing_spans = <Staking as crate::Store>::SlashingSpans::get(&11).unwrap();
+		assert_eq!(slashing_spans.iter().count(), 2);
+
+		// reap_stash respects num_slashing_spans so that weight is accurate
+		assert_noop!(Staking::reap_stash(Origin::NONE, 11, 0), Error::<Test>::IncorrectSlashingSpans);
+		assert_ok!(Staking::reap_stash(Origin::NONE, 11, 2));
 
 		assert!(<Staking as crate::Store>::SlashingSpans::get(&11).is_none());
 		assert_eq!(<Staking as crate::Store>::SpanSlash::get(&(11, 0)).amount_slashed(), &0);
@@ -2705,7 +2772,7 @@ mod offchain_phragmen {
 
 	/// setup a new set of validators and nominator storage items independent of the parent mock
 	/// file. This produces a edge graph that can be reduced.
-	fn build_offchain_phragmen_test_ext() {
+	pub fn build_offchain_phragmen_test_ext() {
 		for i in (10..=40).step_by(10) {
 			// Note: we respect the convention of the mock (10, 11 pairs etc.) since these accounts
 			// have corresponding keys in session which makes everything more ergonomic and
@@ -4092,16 +4159,16 @@ fn test_max_nominator_rewarded_per_validator_and_cant_steal_someone_else_reward(
 fn set_history_depth_works() {
 	ExtBuilder::default().build_and_execute(|| {
 		mock::start_era(10);
-		Staking::set_history_depth(Origin::ROOT, 20).unwrap();
+		Staking::set_history_depth(Origin::ROOT, 20, 0).unwrap();
 		assert!(<Staking as Store>::ErasTotalStake::contains_key(10 - 4));
 		assert!(<Staking as Store>::ErasTotalStake::contains_key(10 - 5));
-		Staking::set_history_depth(Origin::ROOT, 4).unwrap();
+		Staking::set_history_depth(Origin::ROOT, 4, 0).unwrap();
 		assert!(<Staking as Store>::ErasTotalStake::contains_key(10 - 4));
 		assert!(!<Staking as Store>::ErasTotalStake::contains_key(10 - 5));
-		Staking::set_history_depth(Origin::ROOT, 3).unwrap();
+		Staking::set_history_depth(Origin::ROOT, 3, 0).unwrap();
 		assert!(!<Staking as Store>::ErasTotalStake::contains_key(10 - 4));
 		assert!(!<Staking as Store>::ErasTotalStake::contains_key(10 - 5));
-		Staking::set_history_depth(Origin::ROOT, 8).unwrap();
+		Staking::set_history_depth(Origin::ROOT, 8, 0).unwrap();
 		assert!(!<Staking as Store>::ErasTotalStake::contains_key(10 - 4));
 		assert!(!<Staking as Store>::ErasTotalStake::contains_key(10 - 5));
 	});
@@ -4598,3 +4665,36 @@ fn migrate_era_should_handle_errors_2() {
 		assert_eq_error_rate!(Balances::total_balance(&101), init_balance_101, 2);
 	});
 }
+
+#[test]
+fn on_initialize_weight_is_correct() {
+	ExtBuilder::default().has_stakers(false).build_and_execute(|| {
+		assert_eq!(Validators::<Test>::iter().count(), 0);
+		assert_eq!(Nominators::<Test>::iter().count(), 0);
+		// When this pallet has nothing, we do 4 reads each block
+		let base_weight = <Test as frame_system::Trait>::DbWeight::get().reads(4);
+		assert_eq!(base_weight, Staking::on_initialize(0));
+	});
+
+	ExtBuilder::default()
+	.offchain_phragmen_ext()
+	.validator_count(4)
+	.has_stakers(false)
+	.build()
+	.execute_with(|| {
+		crate::tests::offchain_phragmen::build_offchain_phragmen_test_ext();
+		run_to_block(11);
+		Staking::on_finalize(System::block_number());
+		System::set_block_number((System::block_number() + 1).into());
+		Timestamp::set_timestamp(System::block_number() * 1000 + INIT_TIMESTAMP);
+		Session::on_initialize(System::block_number());
+
+		assert_eq!(Validators::<Test>::iter().count(), 4);
+		assert_eq!(Nominators::<Test>::iter().count(), 5);
+		// With 4 validators and 5 nominator, we should increase weight by:
+		// - (4 + 5) reads
+		// - 3 Writes
+		let final_weight = <Test as frame_system::Trait>::DbWeight::get().reads_writes(4 + 9, 3);
+		assert_eq!(final_weight, Staking::on_initialize(System::block_number()));
+	});
+}
diff --git a/substrate/frame/support/src/traits.rs b/substrate/frame/support/src/traits.rs
index 0230937fc4..bd03720220 100644
--- a/substrate/frame/support/src/traits.rs
+++ b/substrate/frame/support/src/traits.rs
@@ -29,6 +29,7 @@ use sp_runtime::{
 };
 use crate::dispatch::Parameter;
 use crate::storage::StorageMap;
+use crate::weights::Weight;
 use impl_trait_for_tuples::impl_for_tuples;
 
 /// An abstraction of a value stored within storage, but possibly as part of a larger composite
@@ -147,12 +148,19 @@ pub trait EstimateNextSessionRotation<BlockNumber> {
 	///
 	/// None should be returned if the estimation fails to come to an answer
 	fn estimate_next_session_rotation(now: BlockNumber) -> Option<BlockNumber>;
+
+	/// Return the weight of calling `estimate_next_session_rotation`
+	fn weight(now: BlockNumber) -> Weight;
 }
 
 impl<BlockNumber: Bounded> EstimateNextSessionRotation<BlockNumber> for () {
 	fn estimate_next_session_rotation(_: BlockNumber) -> Option<BlockNumber> {
 		Default::default()
 	}
+
+	fn weight(_: BlockNumber) -> Weight {
+		0
+	}
 }
 
 /// Something that can estimate at which block the next `new_session` will be triggered. This must
@@ -160,12 +168,19 @@ impl<BlockNumber: Bounded> EstimateNextSessionRotation<BlockNumber> for () {
 pub trait EstimateNextNewSession<BlockNumber> {
 	/// Return the block number at which the next new session is estimated to happen.
 	fn estimate_next_new_session(now: BlockNumber) -> Option<BlockNumber>;
+
+	/// Return the weight of calling `estimate_next_new_session`
+	fn weight(now: BlockNumber) -> Weight;
 }
 
 impl<BlockNumber: Bounded> EstimateNextNewSession<BlockNumber> for () {
 	fn estimate_next_new_session(_: BlockNumber) -> Option<BlockNumber> {
 		Default::default()
 	}
+
+	fn weight(_: BlockNumber) -> Weight {
+		0
+	}
 }
 
 /// Anything that can have a `::len()` method.