How are cooldowns calculated?

I know there are other questions about power recharge and weight, but none of them (that I found) ask or answer this.

At first, I assumed the X% modifier to recharge speed actually meant `your recharge speed is (100+X)% the standard value`. That made sense, because the modifier could positive or negative. Then I realized your recharge speed modifier can go all the way down to -200%, which completely invalidates my assumption.

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Mass Effect tracks cooldowns differently than in most games. Rather than mapping increases / decreases to the base cooldown of the power (where a 100% reduction would be no cooldown), it increases / decreases the number of uses per second.

The Theory is as follows:

Assuming a 5 second cooldown at +100% cooldown would be twice every 5 seconds, or 2.5 seconds, and +200% would be 1.67 seconds.

Reverse would work the same way. -100% cooldowns means once every 10 seconds, and -200% cooldowns means 15 seconds.

!!Science!! Follows:

I decided to pull some numbers from my finished ME3 playthrough save, my Vanguard.

Notes on the Numbers:

• I respeced Shepard, clearing all skills.
• I still had one of the research options for -5% power cooldown.
• All testing took place on the Normandy, which meant no power cooldown gear was applied. I switched my gear to damage or shield bonuses instead, just to be safe.

I have 3 setups for Weight Cooldown Bonuses of -200%, 0%, and 200%.

• -200%: Javelin Sniper Rifle and Claymore Shotgun.

• 0%: AT Raider Shotgun and Locust SMG.

• +200%: Phalanx Pistol.

And here were my numbers. I’m using the skill “Pull”.

• 3.81 seconds
• 3.08 seconds (+25% from Rank 2)

• 1.31 seconds
• 1.21 seconds (+25% from Rank 2)

• 11.8 seconds
• 10.8 seconds (+25% from rank 2)

Other Values: -1% total CDR: 4.07; 0% total CDR: 4.00

Pull has a base cooldown of 4.00. Following our Hypothesis, -200% cooldowns would give a cooldown of 12.00 seconds. Our 5% CDR has a cooldown of 11.8! That’s pretty close to the expected!

Math confirms that this is, in fact, correct: 4 (1.00 + 1.95) = 1 / 11.8!

Additional bonuses, like rank 2 of the ability, stack additively. 1 / 4 (1.00 + 1.7) = 1 / 10.8!

So this works fine and dandy when your malus is a penalty, but what about when you have a bonus? Bonuses are a bit easier – simply divide the cooldown by the bonus %, converted to a decimal.

4 / (1+2.05) (from our 205% weight + research bonus) = 1.31

4 / (1+2.30) (from rank 2) = 1.21

If you have a net bonus, formula is:
[Old Cooldown] / (1+ [Percent Bonus As Decimal]) = [New Cooldown]

If you have a net penalty, formula is:

[Old Cooldown] * (1+ [Percent Bonus As Decimal]) = [New Cooldown]

It’s late, so if someone wants to check my math / make a pretty picture with the formula / math markup, please, be my guest.

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