League of Legends: A Guide to Understanding Ability Haste

With ability haste replacing cooldown reduction, here is what you need to know to understand this new stat in League of Legends.

Cooldown reduction, a fundamental stat since basically the start of League of Legends, is going away with the start of Preseason 11. In its place is a new stat, Ability Haste, which similarly reduces the cooldown of your champion abilities. The problem is that, compared to cooldown reduction (“CDR”), ability haste (“AH”) isn’t as intuitive to understand.

You see, 10% CDR makes sense intuitively. Your ability’s cooldown is 10% less, that means it’s only 90% of the original cooldown. That makes calculating how much a point of CDR is worth much easier.

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For ability haste, though, it’s much harder to grasp how much a point of AH will reduce your ability’s cooldowns. Luckily, I’ve taken the time to go through three different champion abilities on PBE with different levels of ability haste to see how much AH compares to CDR. Let’s dive into some of the essential questions players have about ability haste.

Is Ability Haste Better than CDR?

While CDR stacks multiplicatively, meaning each point of CDR is more meaningful than the last, AH stacks additively. That means you will not gain exponential returns as you add ability haste. In fact, unfortunately, it turns out that ability haste has declining value as you gain more of it, as demonstrated below.

Created by Josh Tyler /

As you can see, as you gain ability haste, your cooldown decreases, just like with the cooldown reduction stat. Unfortunately, the amount of cooldown gained as you gained compared to the last bit of AH you got is less effective, as you can see in the “Percent Change column.” Across all three champions and their abilities, the amount an ability’s cooldown decreases gets smaller. Compare this to old CDR.

Created by Josh Tyler /

As you can see, as you gain more CDR, the amount an ability’s cooldown decreases gets bigger, hence the multiplicative stacking. What’s more, the first 10 AH you get, while roughly as effective as CDR, is still slightly worse than the initial 10% CDR. Considering it then gets less effective as you add more, it’s safe to say that ability haste is a worse overall stat.

So, that begs the question, why did Riot make this change?

How Much Ability Haste Can You Have?

The big reason Riot made this change is that the declining effectiveness of AH allows them to uncap the stat, meaning that you can have as much AH in your build as possible. Just looking at those charts above, if you get to 100 AH you will have 50% CDR, which is more than was possible under the old system. The question is, then, is it even possible to get 100 AH in a build?

The answer, surprisingly, is that it’s not only possible it’s not incredibly difficult. Items that have ability haste have, on average, between 15-20 AH. Many items only have 10, but there are also a decent amount of items with 25 or 30 AH. If you get only two items with 15 ability haste, you’ll have the equivalent of 20-30% CDR.

If, however, you want to completely spec into maximizing ability haste, you can do so. Between runes and items, it’s possible to get up to 200 ability haste. That is equivalent to about 66.7% cooldown reduction.

Now that’s an extreme case where you spec hard into AH with runes, buy Mythic items that grant Legendary items bonus AH, and buy only the items with 20-30 ability haste on them (which isn’t the greatest build). In most of the more standard builds I’ve tried, you can push to about 150 ability haste, which is the equivalent of 60% CDR. So really, pushing for the max ability haste isn’t even worth it, since you need 50 ability haste just to gain 6% CDR at the end of your build.

How Do I Know How Much CDR I Have?

Charting the change in cooldowns to added haste, it became quite clear that AH has a stable link to CDR. While you gain diminishing returns (meaning 10 extra AH doesn’t grant the same amount of CDR depending on how much you have) the CDR breakpoints stay consistent.

All of this is a long-winded way of saying you can know about how much CDR you have based on how much ability haste. So if you are still having trouble moving from CDR to AH, here’s a handy quick conversion guide (note, “~” means approximately).

10% CDR = 10 AH
20% CDR = ~25 AH
30% CDR = ~40 AH
40% CDR = ~70 AH
50% CDR = 100 AH
60% CDR = 150 AH

Does this Change Effect How Much CDR I Get?

No. Generally, if you follow a similar build path to what you did in Season 10 you will get about the equivalent amount of ability haste to give you the CDR you would have gotten. Again, it’s quite easy to get that first 10-20% CDR, you’ll generally get it off one or two items.

If you need more CDR, however, you are going to have to make a deep choice in terms of your itemization. If you get six items, all with the median amount of CDR, you’ll end up with about 60 AH, slightly under 40% CDR. And, yes, ability haste is on a lot of items, but very few items grant more than 20 AH.

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If you’re a mage player who needs lot of spells, then you’re probably going to be able to find a lot of items that get you big chunks of AH (and Mythic items that boost the amount of AH your other items give). If you’re a tank, enchanter, or assassin, however, you’re probably going to need to make some sacrifices to get more than 50 AH just from your standard build.

Luckily, we all have a few months to look into the different builds to see whether we can find that 200 ability haste build. The preseason is upon us, so let the theorycrafting and experimentation begin!

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