**Proc Coefficient** (a.k.a. PC, or Proc Rate) refers to the probability to trigger an effect, such as stun or critical hit. The word *proc* means an effect has been activated.

Proc Coefficient has range between 0 to 1. For example, Glacial Spike's freezing effect has a proc coefficient of 1, meaning it has a 100% chance to freeze a monster when it hits.

## Diablo III[]

All skills have a Proc Coefficient between 0 to 1, which controls the effectiveness of certain "on hit" mechanics which might be applied when those skills are used. If the impact of the effect is measured by a number such as an amount of Life or Damage, that number is multiplied by the Proc Coefficient to determine the final effect - for example Holy Cause heals 1% of total Life per hit with a skill if its Proc Coefficient is 1.0, but only 0.5% of total Life if it's 0.5. If the effect is binary, such as a chance to Stun on hit or other Crowd Control, the chance to trigger on a hit is multiplied by the Proc Coefficient - for example a skill with a Proc Coefficient of 0.3 will turn a stated 10% chance on hit into an actual 3% chance per hit per target.

Generally, Proc Coefficients moderate the effectiveness of:

- standard item Crowd Control affixes
- some passive skills, which may use the phrasing "up to X% chance"
- most Legendary and Set item unique powers which trigger extra damage, many of which were added to the game before
*Diablo III: Reaper of Souls*

They do not apply to:

- the direct effects of active skills themselves; any given Skill Rune description simply states its own chance to apply an effect with that skill
- Legendary and Set item unique powers which increase overall damage or damage to specific skills, or apply a stacking effect; many of these were added or redesigned post-expansion
- Life on Hit, which restores a fixed amount of life per active attack that hit any enemies, regardless of specific skill, as of Patch 2.1.0

With many modern character builds defined by Legendary and Set items which increase damage of skills rather than dealing their own damage, Proc Coefficients are less significant now than before the expansion and its various patches. However, some set mechanics are still affected by Proc Coefficient, and many older Legendary powers may be relatively uncompetitive in part due to Proc Coefficient effects as well as overall strength.

Typically, basic attacks and skills that can only hit one target have Proc Coefficients equal or very close to 1, meaning affects will trigger ("proc") on (nearly) every hit. Some skills, usually those that deal damage independently from the player's actions, like pets, have a proc coefficient of 0, meaning the skill will never trigger "on hit" effects. Damage over time and area of effect skills generally have low proc coeffients, but since they can hit many targets at once, or the same target many times in succession, this balances the overall impact of the effect to be similar to that of a one-target skill.

The Proc Coefficient only affects special effects, not straight attack damage output. Area Damage and many other effects also ignore it. The type or speed of weapons does not affect Proc Coefficient either.

The internal cooldown of some items or skills is a different way to limited a power from being too strong, which may be designed into the power as an alternative or in combination with Proc Coefficient.

### External links[]

- D3 Max Stats - Version 1.x Proc Rates for every class except the Necromancer
- this - Necromancer proc rates

## Diablo IV[]

The current state of Proc Coefficient is unknown in Diablo IV. Before it was removed, the Ancestral Power stat increases the chances of all 'on hit' effects. Although not above 100%, it effectively boosted the Proc Coefficient and the probabilities of all possible procs.