Normally, attack speed runes are reserved for junglers with poor AD scaling or for characters with special on-hits they need to apply. Here we’re going to see how different combinations of damage and attack speed marks/quintessences can affect your dps throughout the game.

Preliminaries

We’re going to use Ashe’s stats because she’s the most basic character and everyone knows her. We’re going to assume basic 21-9-0 masteries, importantly the 4% AS, 12 AD at level 18, and the 3 flat AD. Here are her itemless stats:

The most notable thing about this data is that the max-level dps for both rune setups is almost identical. If this chart were the only thing we were referencing, we would probably end up choosing 15 AD for the superior early game dps, last hitting, and poke potential. However, let’s see how the data looks with the core AD carry items:

This is using 210 bonus attack damage from Infinity Edge, Last Whisper, and Bloodthirster, as well as 70 bonus attack speed from Berserker’s Greaves and Phantom Dancer. Here we have some marked differences. Having attack speed marks and quintessences grants almost 27 extra damage per second. Now you might think, “This difference isn’t that big at all!” And you would be right. But note that there is a difference.

So should I use Attack speed runes?

Answer: Maybe. The major downside of attack speed runes is that they don’t really offer anything during the laning phase in terms of increasing trade efficacy. They also don’t help last hitting in as direct a way as flat damage does. So when should you use them? Attack speed runes rely on more hits to do damage. Because of this, characters who heavily utilize on-hits benefit even more from attack speed bonuses. Examples: Vayne, Kog’Maw, Lucian, Jax, Aatrox, and any time you forsee yourself needing BotRK against a high HP target.

Characters who already come with a damage steriod also benefit more from attack speed. For example, Tryndamere at level 6, with 3 points in Bloodlust:

In the previous chart using Ashe’s stats, the attack speed runes were behind flat AD in dps until level 18. Here, Tryndamere using attack speed runes is already improving his dps before the bonus AD from missing health is applied, which only widens the gap.

The final case for attack speed runes is champions who count their attacks for bonuses, such as Master Yi and Jax.  Yi’s Double-Strike is interesting in that it scales with damage and attack speed, so let’s take a closer look at it:

Well look at that, the dps is almost exactly the same. However, Yi’s Double-Strike also procs on-hits! Using attack speed runes, you get 5 hits in more than a whole second (almost 20%) faster. If you’re playing BotRK Master Yi, attack speed is extremely beneficial. But wait! Master Yi has some AD scaling as well. What now? Alpha Strike will receive an extra 15 or 24 damage from AD runes (depending on the crit). However, with the bonus attack speed, Yi will be able to cast Alpha Strike an entire second sooner, which is more than worth 24 damage.

What about Wuju Style? At level 18, the active and passive will grant… 5 damage, or around 30% of 15. On Tryndamere we already demonstrated that multiplying a pre-existing damage bonus (here, the 10/15/20/25/30 true damage on Wuju Style) by increased attack speed results in a greater bonus than flat damage.

Master Yi’s Ult, however, increases his attack speed. This steroid benefits more from flat damage than more attack speed! Let’s look at a level 18 ulting Yi.

Now being able to build full dps Yi isn’t exactly common, but I implemented it as a thought exercise. With all the items, attack speed still wins. With no items (more reminiscent of a tankier Yi), flat AD wins by less than 2%. This advantage is more than mitigated by on-hits.

Jax is an interesting case as well. Every time he attacks, he gets attack speed, stacking up to six times. Having attack speed runes lets you get more attack speed faster, but in the end do you want more damage for all this attack speed you get for free? Let’s find out.

This Jax is without masteries. I chose level 7 because a) Jax now has his ult and b) the AS bonus on-hit improves to 8% per hit at level 7, to give AD a little more oomph in the calculation. Before you consider Jax’s ult, 15 AD Jax is slightly ahead. At level 1, Jax’s ult adds 100 magic damage to every third attack. So that we can calculate approximate dps, I’m going to split the 100 damage across 3 attacks, effectively giving each attack 33 more damage. Here’s a chart with the ult damage spread across his attacks:

The end result of this is that Jax, with his ult, has more dps before and after his passive has stacked if he uses attack speed runes. Using attack speed runes also accelerates the accumulation of his passive, giving it even more of an advantage.

From these we can safely say that attack speed is superior to flat damage in terms of raw dps, which is applicable to committed fights and jungling (10 bonus damage from Hunter’s Machete also benefits from AS).

When shouldn’t I use attack speed runes?

Whenever your champion has good AD scaling, an attack speed buff, and/or you’re going to do a lot of poking in-lane. Characters like Graves, Tristana, and Caitlyn come to mind. Graves has abilities with decent AD scaling. Both he and Tristana come with AS steroids, which is greater benefited from flat damage runes. Caitlyn has great range, decent scaling, and pokes a lot, one auto-attack a time, which also favors flat damage.

The other situation where AD runes are especially good is if you need to do a lot of last hitting under tower. Going back to Ashe, let’s look at what happens if you had attack speed marks and damage quintessences to assist in last hitting under the tower:

This is between the previous results of 541 dps (15 AD) and 568 dps (25% AS). So if you want to increase your dps and maintain some last hitting power, perhaps with a Doran’s Blade, that’s entirely possible.

Summary:

Attack speed runes increase your raw dps in almost all cases. However, you sacrifice some last hitting, poke potential, and AD scaling on abilities. If your champion has an AD buff or on-hits, generally you will want AS runes. If your champion has an AS buff or AD-scaling abilities, you generally want AD runes.