Ultimate Guide to League of Legends Ability Haste vs. Cooldown Reduction

Ability Haste increases how often an eligible ability can be cast; it does not subtract the same number of seconds from every cooldown. Use new cooldown = base cooldown ÷ (1 + Ability Haste ÷ 100). At 100 Ability Haste, a 10-second ability drops to 5 seconds, which is equivalent to 50% old-style Cooldown Reduction (CDR). It is not 100% CDR. Knowing that distinction helps you compare builds without treating haste points like percentages.

Ability Haste vs. Cooldown Reduction: What Changed?

Riot replaced the old CDR stat with Ability Haste for Preseason 2021. CDR was written as a percentage of cooldown time removed: 40% CDR turned a 10-second base cooldown into 6 seconds. Because each additional point of CDR increased cast frequency more sharply as you stacked it, the old system used a cap. Riot designed Ability Haste around a different measure: each point adds 1% more ability casts over the same amount of time, before other effects.

That makes AH additive in cast frequency, while its effect on the displayed cooldown follows a fraction. More haste always shortens the cooldown, but each extra point removes fewer seconds than the previous one. The ability still becomes more available at a steady rate per point of AH.

Two circular ability timers show a full cooldown ring beside a ring with less time remaining — A cooldown ring loses a smaller amount of time as the remaining cooldown gets shorter.

How to Calculate an Ability Haste Cooldown

Start with the ability’s base cooldown at its current rank, then divide by one plus total Ability Haste expressed as a decimal. For example, with 60 AH and a 12-second base cooldown: 12 ÷ (1 + 0.60) = 7.5 seconds. This is the standard calculation for an eligible cooldown; ability-specific effects, cooldown refunds, charges, and resets can change what happens in a real match.

Formula: cooldown after AH = base cooldown ÷ (1 + AH/100). To convert an old CDR percentage into equivalent AH, use AH = 100 × CDR ÷ (100 − CDR). So 40% CDR corresponds to about 66.7 AH, not 40 AH.

Base cooldown	50 AH	100 AH	200 AH	300 AH
10 seconds	6.67 seconds	5 seconds	3.33 seconds	2.5 seconds
20 seconds	13.33 seconds	10 seconds	6.67 seconds	5 seconds
5 seconds	3.33 seconds	2.5 seconds	1.67 seconds	1.25 seconds

For comparison, 40% old CDR would make those same base cooldowns 6, 12, and 3 seconds. The table also corrects a common mistake: at 300 AH, a 10-second ability has a 2.5-second cooldown, not roughly 3.1 seconds. Riot’s official Patch 10.23 notes explain the change and the relationship between haste and cast frequency.

A fantasy game ability bar contrasts one spell cast with a sequence of repeated casts — More Ability Haste means more potential casts in the same time window; it does not mean every haste point removes a fixed number of seconds.

When Is Ability Haste Worth Building?

There is no universal “best AH build” for every champion or patch. Treat haste as one part of a build decision, alongside damage, defense, mobility, mana or energy needs, and the match’s threats. A high number on the stats panel is useful only if it lets you land another meaningful spell when it matters.

Several blue stat icons converge on one ability icon to represent haste added from eligible sources — Eligible Ability Haste bonuses from multiple sources contribute to your total, as shown by the current in-game stat panel.

Use this quick build check

Find the limiting cooldown. Identify the spell you need again during a normal trade, skirmish, or teamfight. If it is still unavailable when the next useful window opens, haste may help.
Check whether another cast is realistic. Haste does not provide mana, guarantee that a target stays in range, or bypass a spell’s charges and special rules. Consider whether you can actually use the extra cast.
Compare the trade-off. A haste purchase may give up burst damage, durability, penetration, movement, or a defensive effect. Choose the stat that solves the bigger problem in that game.
Recheck the current patch. Item stats and balance change. Riot’s Patch 26.20 notes, published October 6, 2026, lowered Hextech Rocketbelt’s Ability Haste from 20 to 10. Use the live item tooltip and current patch notes instead of copying an old build list.

A champion faces a blue ability-haste setup and a separate panel of damage, defense, health, and movement icons — The useful choice depends on whether another spell cast is worth more than the other stats available to your champion.

Special Cooldowns: Ultimates and Summoner Spells

Ability Haste applies to eligible champion ability cooldowns, but do not assume every timer uses the same stat. Some effects name Ultimate Haste specifically, while Summoner Spell Haste is a separate stat Riot lists in item notes. Read the full tooltip to see which cooldown an effect changes. The official Patch 14.1 notes show Summoner Spell Haste as a distinct stat. Cooldown refunds, charge recharge, and resets are also not automatically interchangeable with ordinary AH.

Ability Haste is not subject to the old 40% CDR ceiling as a direct stat, but that does not make every theoretical value available or every cooldown reducible without limit. Item availability, runes, champion rules, game mode, and the current patch all matter.

Quick Answers

Is 100 Ability Haste the same as 100% CDR?

No. 100 AH doubles cast frequency and halves the standard cooldown, so it is equivalent to 50% CDR.

Does 10 Ability Haste reduce a cooldown by 10%?

No. Ten AH gives 10% more casts over the same time. A 10-second cooldown becomes about 9.09 seconds, which is a 9.09% time reduction.

Does Ability Haste reduce Summoner Spell cooldowns?

Do not rely on ordinary AH for that. Check whether you have Summoner Spell Haste or a specific effect that says it affects a Summoner Spell.

Sources and Patch Reference

Riot Games introduced the stat in its Preseason 2021 item goals and documented the mechanics in the Patch 10.23 notes. For current item values, consult the Patch 26.20 notes and the in-game tooltips.