Skill Cooldown Calculator
Find the effective cooldown of any game skill after applying Cooldown Reduction (CDR). Use it to optimize ability rotations and compare gear choices in RPGs or MOBAs.
About this calculator
Cooldown Reduction (CDR) is a stat in many games that shortens the wait time between skill uses. The effective cooldown is calculated as: effectiveCooldown = baseCooldown × (1 − cooldownReduction / 100). Here, baseCooldown is the skill's cooldown in seconds before any CDR is applied, and cooldownReduction is the percentage reduction from items, talents, or runes. Dividing CDR by 100 converts it to a decimal multiplier, and subtracting from 1 gives the remaining fraction of the original cooldown. Most games cap CDR at 40% or 45%, so inputs beyond the cap won't produce in-game results. This formula is standard across games like League of Legends, World of Warcraft, and Diablo.
How to use
Imagine your skill has a base cooldown of 12 seconds and you have 30% CDR from your items. Step 1: Convert CDR to a decimal — 30 / 100 = 0.30. Step 2: Subtract from 1 — 1 − 0.30 = 0.70. Step 3: Multiply by the base cooldown — 12 × 0.70 = 8.4 seconds. Your skill's effective cooldown is 8.4 seconds. That's 3.6 seconds saved per cast — significant over a long fight with many rotations.
Frequently asked questions
How does cooldown reduction affect skill uptime in games?
Cooldown reduction directly increases how often you can use a skill within a given time window, which is called uptime. With 0% CDR, a 10-second cooldown skill can be cast 6 times per minute. At 40% CDR, the effective cooldown drops to 6 seconds, allowing 10 casts per minute — a 67% increase in usage frequency. Higher CDR is especially valuable for skills with strong effects, making it a priority stat for ability-focused builds.
What is the CDR cap and why do most games impose one?
Most games cap CDR at a specific value — commonly 40% or 45% — to prevent skills from becoming available almost instantly, which would break game balance. Without a cap, stacking CDR items could reduce cooldowns to near zero, making cooldowns meaningless as a balancing mechanic. Game designers use the cap to ensure cooldown-dependent skills retain strategic timing. Always check your specific game's documentation to know where the cap sits before stacking CDR past a certain point.
Why does cooldown reduction give diminishing returns in some games?
Some games implement CDR with diminishing returns, meaning each additional percentage of CDR reduces the cooldown by a smaller absolute amount than the last. This is a design choice to prevent CDR from being overwhelmingly powerful. In contrast, the simple linear formula used here (baseCooldown × (1 − CDR/100)) does not have diminishing returns — each 1% CDR saves the same fraction of the base cooldown. If your game uses a diminishing-returns formula, this calculator's results will overestimate the benefit of high CDR values.