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Procs per minute (PPM) describes how a given proc mechanic functions. It is often used to contrast a game mechanic with one that uses "procs per hit" (PPH).
In World of Warcraft Edit
PPM vs. PPH Edit
In World of Warcraft, PPH is the percent chance of a proc occurring each hit. PPH benefits greatly from faster hits.
PPM scales to PPH according to weapon speed. Here is the formula:
 PPH = (Weapon speed) / (60 / PPM)
which is the same as:
 PPH = Weapon speed * PPM / 60
This gives the percentage chance that the proc will be triggered each hit. Note that PPM is an average, not a guarantee.
PPM and Haste Edit
The speed used for calculating the PPH (Proc Per Hit) chance is the basic weapon speed, not the characters hasteaffected hit speed. This means the probability of a proc is not lowered or increased by haste. What haste does is increase the total amount of melee hits per time and thus the total amount of procs.
Instant attacks Edit
The PPM rate of a given effect is based on autoattacks ("white damage" attacks) made with that weapon. However, an effect on the mainhand weapon can proc more often than its PPM rating, as instant attacks (Sinister Strike, Overpower, etc.) are all assumed to be made with the main hand, and therefore can trigger the proc.
In addition, because instant attacks use the calculated PPH rate based on the weapon speed, yet are not themselves restricted by the weapon speed, a slower weapon will result in more total procs.
For example, a Warrior has Crusader (PPM of 1) on a 2.0speed and a 2.5speed weapon. These calculations assume ample Rage and no misses.
 Weapon 1 (speed 2.0): 30 white hits per minute, so PPH is 1/30.
 Weapon 2 (speed 2.5): 24 white hits per minute, so PPH is 1/24.
Each minute, the Warrior also does 10 Bloodthirsts, 6 Whirlwinds, and 4 Overpowers, for a total of 20 instant attacks.
 Weapon 1 (PPH 1/30): 50 hits (20 instant + 30 white), so actual PPM is 50/30 = 1.67.
 Weapon 2 (PPH 1/24): 44 hits (20 instant + 24 white), so actual PPM is 44/24 = 1.83.
Therefore, the slower the weapon you wield in the main hand, the more often any PPMrated ability on it will proc, assuming you use any special attacks that can trigger the proc.
All these calculations are made with no Flurry included.
PPM Rates Edit
 [Formula: Enchant Weapon  Berserking]: 1.698 (does not appear to proc from instant attacks)
The subject of this article was removed from World of Warcraft after the Mists of Pandaria cleared.
