Procs Per Minute
Overview
Procs Per Minute (PPM) is the "average" number of times per minute an enhancement's special effect will attempt to fire. This mechanic is used by all enhancements with procs.
Procs Per Minute are calculated off the base recharge + activation time of a power, not its final enhanced or buffed number. So a power that takes 12 seconds to recharge and activate will have the same PPM as the same power enhanced and buffed enough to halve its recharge.
Calculating Chance to Proc
The current formulae used by the game:
If power is a click: PPM * ((Base Recharge Time + Time To Activate) / (60 * Area Factor))
If power is not a click: PPM * ((Activate Period) / (60 * Area Factor))
When accounting for powers that potentially can effect multiple targets and the proc potentially hitting off each target, the game discounts the probability of proc-ing off any one target by an Area Factor. The current way to calculate this number:
Area Factor = 1+(0.15*Radius)-(0.011*Radius*(360-Arc)/30)
Two things to note here:
- Single target powers have a radius of 0 which collapses the Area Factor to 1.
- Area Factor applies regardless of how many you actually hit. When using AoE and cones on single targets, proc performance will be significantly lower than with comparable single target powers.
Guaranteed Proc
Single Target
The formula for calculating the required recharge + activation time to achieve a 100% proc chance is 60/PPM. For instance, if an enhancement has a 5PPM rate, then 60/5=12 seconds; a power with a base recharge + activation time of 12 seconds will guarantee a proc every time it executes, even if the power's final recharge is less. If an enhancement has a 1.5PPM rate, then a power needs a base recharge + activation time of 40 seconds to guarantee a proc.
Note that non-click powers cannot change their "activate period", so their chance to fire will always be the same, even if the power can be slotted or buffed with recharge.
| 1PPM | 60 seconds | 4PPM | 15 seconds |
|---|---|---|---|
| 1.5PPM | 40 seconds | 4.5PPM | 13.33 seconds |
| 2PPM | 30 seconds | 5PPM | 12 seconds |
| 2.5PPM | 24 seconds | 5.5PPM | 10.91 seconds |
| 3PPM | 20 seconds | 6PPM | 10 seconds |
| 3.5PPM | 17.14 seconds | 6.5PPM | 9.23 seconds |
Cone/Area of Effect
The formula for calculating the required recharge + activation time to achieve a 100% proc chance is (60 * Area Factor)/PPM, where Area Factor is 1+(0.15*Radius)-(0.011*Radius*(360-Arc)/30).[1] Note that when Arc is 360 degrees (which is true for any non-Cone AoE) the Area Factor simplifies to 1+(0.15*Radius).
A refactored equation for the Area Factor which converts the decimal fractions into long-form with a single linear order of operations and no decimals is (((((Arc-360)*11)+4500)/30000)*Radius)+1.
Developer Comments
Arbiter Hawk explained it in several posts on the official forums regarding the PPM system:
This is a bit of a trick question - these procs that you mention function like store-bought IO procs, so their chance to proc with any given power activation fluctuates with the power's recharge time and some other factors. The long and short of it is that you should put the proc in a power you like to use, but this Proc-per-minute functionality does not advantage, say, Neutrino Bolt over X-Ray Eyes, if you like using X-Ray more. Slot the procs into attacks that you use, and you'll see them go off fairly regularly.
It is not limited to its displayed number of procs per minutes - that is representative of the average number of times it will proc over a minute if you use a single-target power every time it comes off recharge. You can still "get lucky", roll high numbers on the under-the-hood dice, and get many more than 4 procs in a minute. Its just that instead of a flat 20% chance to proc (which gives higher proc uptime per minute to a power that can be used more times per minute), the chance of proc'ing is now variable with the recharge (and other special factors) of the power that you're enhancing.
It's base recharge time. If you have a single target attack slotted with a 2 ppm IO, the power would need to have a 30 second recharge to have a 100% proc chance. You could then IO it to ~100% recharge and combine that with 100% global recharge bonus to get the power's recharge down to 10 seconds, and it would still have that 100% proc chance. This is how all of the store-bought IO set procs work, as well as the ATO procs that are not global bonuses. This changes the math on "optimal proccing" significantly from the traditional "flat rate" approach, and causes the performance delta of optimal and non-optimal to be much smaller, so you can really slot these in any power you use and you will see them be effective.