Cooldown Reduction Calculator
Calculate effective ability cooldowns after CDR stacking.
See diminishing returns and optimal CDR breakpoints.
Effective Cooldown
Cooldown Reduction (CDR) shortens the time between ability uses.
Percentage CDR formula:
Effective Cooldown = Base Cooldown × (1 − CDR/100)
Example: 10s cooldown with 40% CDR = 10 × 0.60 = 6 seconds
CDR has diminishing returns:
- Going from 0% to 10% saves 1s on a 10s cooldown
- Going from 30% to 40% saves 1s on a 10s cooldown
- Going from 40% to 50% saves 1s… but is harder to get
Ability Haste (used in League of Legends):
Effective Cooldown = Base Cooldown × (100 / (100 + Ability Haste))
Ability Haste scales linearly — each point gives equal benefit. 100 Ability Haste = 50% CDR equivalent.
CDR caps vary by game (commonly 40% or 45%).