Each skill has its own cooldown. Using one also starts a global cooldown, so you cannot fire another skill until that clock finishes. Cooldown reduction shortens the skill's own wait. It does not change the global cooldown.
Numbers from DS_B.0.4.23.
At a glance
Direct answers
How is skill cooldown calculated?
Take the cooldown on the skill. Divide it by (1 + Cooldown Reduction / 100). A 0 result, or a divisor that is not greater than 0, leaves the table cooldown unchanged.
How is cooldown lowered?
Cooldown Reduction is the stat that shortens a skill's own cooldown. Willpower adds +0.3 per point. Inscriptions, blessings and a few other effects add more. A negative value lengthens the wait.
Is global cooldown affected by cooldown reduction?
No. After a skill, global cooldown is 5 s. Cooldown reduction never enters that path. A new global cooldown only replaces the remaining one when it is longer.
Skill cooldown
Most skills use this divide. The table uses the most common cooldowns in this build, and the reduction amounts the game actually grants.
Example: a 15 s skill with +20 cooldown reduction waits 12.5 s.
| Table cooldown | No reduction | +10 | +20 | +30 |
|---|---|---|---|---|
| 15 s | 15 s | 13.64 s | 12.5 s | 11.54 s |
| 20 s | 20 s | 18.18 s | 16.67 s | 15.38 s |
| 12 s | 12 s | 10.91 s | 10 s | 9.231 s |
| 10 s | 10 s | 9.091 s | 8.333 s | 7.692 s |
| 30 s | 30 s | 27.27 s | 25 s | 23.08 s |
Diminishing returns
The formula is not one-for-one. The first points of cooldown reduction cut more wait than the same amount added later.
The graph is leftover wait, as a share of the table cooldown. With none, you wait the full time. At 100 cooldown reduction you wait half.
On a 15 s skill, the first +20 saves 2.5 s. The next +20 only saves 1.786 s.
Will Power is slow on this curve: each point is +0.3. Inscriptions jump +10, +20, +30 in one go.
Will Power alone, on a 15 s skill. That is the most common table cooldown.
| Will Power | Cooldown reduction | Wait on a 15 s skill | Saved vs none |
|---|---|---|---|
| 0 | 0 | 15 s | 0 s |
| 10 | +3 | 14.56 s | 0.4369 s |
| 20 | +6 | 14.15 s | 0.8491 s |
| 30 | +9 | 13.76 s | 1.239 s |
| 40 | +12 | 13.39 s | 1.607 s |
| 50 | +15 | 13.04 s | 1.957 s |
Global cooldown
Using a skill starts a 5 s global cooldown on that unit. Other skills wait for it. The amount is the combat table value, copied onto the unit. Cooldown reduction is not applied.
If a shorter global cooldown would land while a longer one is still running, the remaining wait is kept. Swapping equipment in combat starts a 10 s global cooldown on the same clock.
A skill whose own table cooldown is 0 still starts the global cooldown when that skill's cooldown check succeeds.
What lowers it
Every effect that writes cooldown reduction is in the table. Cooldown Reduction itself is built from Willpower first, then any extra percent modifiers.
On top of those effects, each point of Willpower adds +0.3 cooldown reduction.
| Source | Cooldown reduction | How you get it |
|---|---|---|
 High-grade Cooldown Reduction Inscription | +30 | Inscription |
 Mid-grade Cooldown Reduction Inscription | +20 | Inscription |
 Low-grade Cooldown Reduction Inscription | +10 | Inscription |
 Porter | -10 | Background |
 Cooldown Reduction | +30 | Granted by Ebb And Flow, Life Burst. |
 Taking Skill Cooldown Potion | +30 | No obtainable source in this build. Also in the data: Skill Cooldown Potion. |
 Perhaps a Harp | +20 | No obtainable source in this build. |
 Goddess' Blessing (Skill Cooldown) | +10 | No obtainable source in this build. |
Skills that use attack speed
A few skills divide their table cooldown by attack speed instead of by (1 + cooldown reduction / 100). Cooldown reduction does not enter that path. A skill whose table cooldown is 0 never reaches either divide.
| Skill | Table cooldown |
|---|---|
 Run | 1 s |
 Goblin Flee | 10 s |
 Resurrection | 10 s |
 Earth Crash | 15 s |
 Goblin Curse | 15 s |
 Blood Rain | 16 s |
Under the hoodhow the code does it
- Skill cooldown is the table cooldown divided by (1 + cooldown reduction / 100), unless the attack-speed flag is set.
- If that divisor is not greater than 0, the table cooldown is used unchanged.
- Global cooldown duration is the combat table value stored on the unit. A positive global-cooldown apply uses that stored value. The apply amount is only a sign. Cooldown reduction is not read.
- A new global cooldown replaces the remaining one only when it is longer.
Related: Combat Formulas · Talents · Equipment Effects.