Ability Haste in LoL: Formula, CDR Conversion, and Cap

Ability Haste (AH) is the stat that reduces your ability cooldowns. Each point speeds up your casting rate by 1%, so 100 AH lets you cast twice as fast as 0 AH (equivalent to 50% old-style cooldown reduction). It replaced Cooldown Reduction in the 2021 preseason on patch 10.23. Unlike CDR's hard 40% cap, AH stacks with no diminishing returns up to its cap of 500. Full AH-to-CDR conversion table below.

How Ability Haste Works

Ability Haste reduces the cooldown of your champion abilities. The exact formula is:

New Cooldown = Base Cooldown × 100 / (100 + AH)

Equivalently, the percent cooldown reduction at any AH value is:

CDR% = AH / (100 + AH)

The intuition the wiki and most pros use: AH is "attack speed for abilities." Each point of AH adds 1% to your casting rate. 50 AH means you cast 50% more often. 100 AH means you cast twice as often. 200 AH means you cast three times as often. The cooldown number on your ability shrinks hyperbolically, but the rate at which you cast scales linearly.

That linear scaling is the entire reason the stat exists.

A worked example: a 12-second Q at 0 AH stays at 12 seconds. At 20 AH, it becomes 12 × 100 / 120 = 10 seconds. At 50 AH, it becomes 12 × 100 / 150 = 8 seconds. At 100 AH, it becomes 6 seconds. The cooldown gets shorter, but the difference between consecutive AH levels gets smaller in raw seconds. What stays constant is how much extra DPS each point of AH adds.

Ability Haste to CDR Conversion Table

The table below shows how AH translates to old-style percent cooldown reduction, plus the actual cooldown on a 10-second ability for reference.

A few values worth memorizing: 25 AH is exactly 20% CDR, 67 AH matches the old 40% CDR cap, and 100 AH halves your cooldowns. Most full builds end up between 30 and 80 AH, so the realistic range you'll feel in a game is the top of the table, not the bottom.

Why Ability Haste Replaced Cooldown Reduction

The old CDR stat had a math problem. Going from 30% to 40% CDR was much stronger than going from 0% to 10% CDR, because each percentage point removed a larger share of the remaining cooldown. Reaching 40% CDR effectively gave you 67% more casts per second, but reaching 10% CDR only gave you 11%. This is geometric scaling.

That non-linearity forced two design problems on Riot:

• A hard 40% cap was needed because uncapped CDR would have been broken at high stacks.
• Item designers had to fight the cap. Once a build hit 40%, every additional CDR item was wasted, so late-game items couldn't carry CDR as a meaningful stat.

Ability Haste flips that. Each point of AH adds the same 1% to your casting rate, so the stat scales linearly with damage-per-second. There's no cap to fight (other than the unreachable 500 hard cap), so items at every price point can carry AH and the value is always the same. Riot Scruffy framed it directly in the preseason 2021 announcement: AH works "just like Armor or MR. You can get as much of it as you want and the value is always the same."

Ability Haste vs. Basic Ability Haste vs. Ultimate Haste

The HUD stat panel shows a single number, but there are three different haste pools that affect champion abilities. They stack additively with each other, but each comes from different sources.

Ability Haste

The default. Affects all four abilities (Q, W, E, R). This is what every "ability haste" item gives. Stacks additively. Hard-capped at 500.

Basic Ability Haste

Affects only Q, W, and E. Does not affect the ultimate. Used to be a niche keystone stat; now mostly comes from Legend: Haste (precision rune tree) and a few champion-specific passives. Combined with regular AH, the total cap on basic abilities is still 500.

Ultimate Haste

Affects only the ultimate (R). Comes from runes like Ultimate Hunter, items like Experimental Hexplate, Malignance, and Zeke's Convergence (the active-cast ult bonus), and champion passives like Kindred. Stacks additively with regular AH on the R cooldown only. Combined cap on the ultimate is 500.

Two other haste pools exist that are easy to confuse with AH but are entirely separate: item haste reduces active item cooldowns (Stopwatch, Hextech Rocketbelt active, Galeforce active) and comes from runes like Cosmic Insight. Summoner spell haste reduces Flash, Ignite, Heal, and the rest, also primarily from Cosmic Insight. Ability Haste does not affect either.

Practical answer to the most common confusion: regular AH affects your ultimate. You don't need ultimate haste to make your R come back faster. Ultimate haste is just an additional pool that stacks on top.

Where Ability Haste Comes From

The exact item list shifts every patch, but the structure is stable. Most full builds pull AH from three places:

• Items. Cheap components like Kindlegem, Fiendish Codex, and Caulfield's Warhammer give 10 AH at the 800-1050g range. Mid-tier completed items like Black Cleaver, Frozen Heart, Hextech Rocketbelt, and Moonstone Renewer give 20 AH. The highest-AH items on the Rift sit at 25 AH (Cosmic Drive, Horizon Focus, Seraph's Embrace).
• Boots. Ionian Boots of Lucidity grant 10 AH plus reduced summoner spell cooldowns. The default boot choice for any caster who isn't forced into resistances or movement.
• Runes. Transcendence (Sorcery tree) gives 5 AH at level 5, 5 more at level 8, and 5 more at level 11, for a total of 15 AH by mid-game. Stat shards on the rune page can add another 8 AH each.

One point of AH is internally valued at 50 gold by item designers, which is why you'll see roughly that ratio across components. Kindlegem at 800g gives 10 AH plus 200 HP; Caulfield's Warhammer at 1050g gives 10 AH plus 30 AD.

When to Build Ability Haste

AH is strongest on champions whose damage or utility output scales with cast frequency rather than per-cast damage. The two clearest cases:

• Ability-spam mages and bruisers. Cassiopeia, Ryze, Viktor, Sett, Renekton, anyone whose kit fires every few seconds. More AH directly means more poke, more waveclear, more sustained teamfight pressure. These champions often build Black Cleaver, Cosmic Drive, or Horizon Focus specifically for the AH.
• Utility champions whose ult or key spell defines fights. Engage tanks (Malphite, Sejuani), enchanters (Lulu, Karma), and ult-reliant junglers want low ultimate cooldowns. They stack AH plus ultimate haste to get one extra ult per teamfight cycle.

AH is weaker on:

• Auto-attack reliant champions. Most marksmen and on-hit fighters get more from attack speed, crit, and lifesteal than from AH. A few exceptions exist (Senna, Aphelios, Lucian) where ability casts matter more than autos.
• One-shot assassins. Zed, Talon, and Khazix care about per-cast damage, not cast frequency. Lethality and AD scale their burst better than AH does.

Is There an Ability Haste Cap?

Yes, but you'll never hit it. The hard cap is 500 AH (83.3% effective CDR). The highest AH a real Summoner's Rift draft build has reached in recent patches is around 297 AH, achieved with a specific champion plus full haste-stacking items, runes, and team buffs. Normal builds top out between 30 and 80 AH. URF mode applies 400 AH as a baseline buff to every champion, which is why URF cooldowns feel non-existent.

The takeaway: there's no functional cap to plan around. Build as much AH as your slots can spare, and it will keep paying out at the same rate the whole way up.

Ability Haste Quick Answers

• Does Ability Haste affect ultimates? Yes. Regular AH reduces the cooldown of your R alongside Q, W, and E. Ultimate Haste is a separate, additive bonus that affects only the ultimate.
• Does Ability Haste reduce item active cooldowns? No. That's Item Haste, a separate stat from runes like Cosmic Insight.
• Does Ability Haste reduce summoner spell cooldowns? No. That's Summoner Spell Haste, mainly from Cosmic Insight and Ionian Boots of Lucidity.
• Is 100 AH the cap? No. 100 AH is the point where your cooldowns are halved. The hard cap is 500.
• Is Ability Haste better than CDR was? For the player, late-game stacking feels stronger because there's no cap. For the game, it's better because each point is the same value, which makes balance easier and lets every item carry the stat.