| Rank | Chance |
|---|---|
| 1 | 2% |
| 2 | 4% |
| 3 | 6% |
| 4 | 8% |
| 5 | 10% |
Spell description
10% chance to receive an extra attack on your next swing for 8 seconds or 4 attacks, whichever comes first, whenever hit by damage.
Overview
Reckoning is a talent in the Protection tree, you will need to spend 25 points in Protection to max it.
Usage
Reckoning's mechanics have changed in patch 2.0.1. Instead of giving the Paladin a 100% chance to gain an extra attack upon being critically hit, it now has a 10% chance of triggering when hit with any damage, allowing the paladin's next 4 swings to generate an extra attack (fading in 8 seconds). This change has been criticised mostly by Paladins, stating that it reduces the Protection Paladin's burst damage potential because up to 5 reckoning charges could be stored. This method would be especially used in PvP where critical hit chances are inflated. Although Reckoning's damage capabilities in PvP were vastly reduced, it has shifted this talent greatly into the PvE arena, reflecting the changes made to the Paladin's Protection tree to become more PvE tanking-oriented.
It now has a 10% chance of triggering when being hit with any damage, meaning the more sources of damage taken by the paladin, the higher chance the Paladin's damage will double, dramatically increasing threat towards the target. This is the origin of Paladin AOE Tanking. Together with the talents 
[Redoubt] and 
[Ardent Defender], damage mitigation of the Paladin from a drop in hit points increases dramatically, and the Paladin swings so often from Reckoning charges that with the use of 
[Seal of Light] and 
[Judgement of Light], can regenerate health faster than the Paladin can lose. This also potentially double's the Paladin's damage output, so no offensive Seals can be used to still obtain devastating results.
The extra attacks do not affect proc rates, so the Paladin will get twice as much out of seals, judgements, and enchantments. This means Holy Vengeance can be applied twice as fast when using 
[Seal of Vengeance] (Alliance only). Only one Seal does not follow this rule - 
[Seal of Command]. Although the Paladin gets two melee swings at a target per Reckoning charge, Seal of Command damage can only proc at the first swing, meaning it cannot proc twice in a Reckoning charge.
Reckoning triggers off of any damage, including spells, melee attacks, ranged attacks, and environmental effects, such as campfire damage.
Analysis
In short, "As long as your weapon is 2.0 or slower, it makes no difference for Reckoning", Elandris at "Reckoning: Why weapon speed doesn't matter"
Proof:
Assume the time when reckoning is triggered is a uniform distribution over one's combat duration. Let the average weapon damage be D, speed be X, the number of swings in 8 seconds be N. Denote the floor of a real number z be [z] in the following. Then we have:
N = [8 / x]
N * x <= 8
(N+1) * x > 8
The probability (p1) of having N swings is: (It procs (8 - N * x) after a swing.)
p1 = ((N+1) * x - 8) / x
And the probability (p2) of having N+1 swings is:
p2 = (8 - N * x) / x
Therefore, on average, the number of extra swings (M) is:
M = N * p1 + (N+1) * p2
= (N2*x + N*x - 8*N + 8*N + 8 - N2*x - N*x) / x
= 8 / x
Hence the average total damage (T) caused by reckoning is:
T = D * (8 / x)
= (D / x) * 8
= "weapon's DPS" * 8
Example:
Given a weapon with average damage 100, and speed 2.5 (and its DPS accordingly be 40). Then:
N = [8 / 2.5] = 3,
p1 = 2 / 2.5,
p2 = 0.5 / 2.5,
M = 3 * 2 / 2.5 + 4 * 0.5 / 2.5 = 8 / 2.5,
T = 100 * (8 / 2.5) = (100 / 2.5) * 8 = 40 * 8.