Which tenacity stacks, and which doesn't?

Risen29·Mar 28, 2018·1 votes·1,595 views

I was testing in the practice tool.

I had the precision rune that gives 20% tenacity, and the resolve rune that gives 20% tenacity when both my summoners are on cooldown.

I had Merc Treads, 30% tenacity.

But I didn't have 70% tenacity. I had 55%.

How does strength of Iron (25% tenacity) and steraks (30% tenacity) fit into all this?

My goal is to have the maximum CC resistance possible with this build, but I don't want to waste runes and gold on things that aren't going to stack.

4 Comments

Ok sure but whyMar 28, 20182 votes

Tenacity works on the amount of tenacity you don't have.

So like, you start off with 0 tenacity.

Then you get an item that gives you 40% tenacity. Woo hoo! You still get stunned for 60% of the duration.

Now, imagine you get an item that gives you 50% tenacity. That 50% is gonna cut your current 60% stun time in half, leaving you to get stunned for 30% of the duration instead. That's how %resistance penetration works, too.

So in short, 40 + 50 = 70. You're welcome!

C9 Squeeky Mar 28, 20181 votes

It sounds like it goes like this: 30% (merc treads), 20% multiplier from Legend (1.2 x 30% = 36%), then I guess Unflinching are addictive for 56%.

This is just a guess, some things are additive, some are multiplicative. Sadly, I don't know which items give add or multiply.

AlienPrimateMar 28, 20181 votes

Tenacity is calculated by taking the inverse of each value and multiplying them together to find the effect you receive from CC rather than your resistance to it. It functions this way to avoid people reaching cc immunity. In your example:

(1 - 0.2) x (1 - 0.2) x (1 - 0.3) = 0.448 effect receivied

Then you take the inverse of this to find your tenacity. 1 - 0.448 = 0.552

Adding in Sterak's and iron elixir gives

1 - (1 - 0.2) x (1 - 0.2) x (1 - 0.3) x (1 - 0.25) x (1 - 0.3) = 0.7648= 76% tenacity

Damage reduction from multiple sources is found using the same method. For example, Warwick with his E, phantom dancer, the new Locket, and Death's dance could be plugged into the same formula from above.

If you don't like math, just think of it this way. Morgana hits you with her Q. Each instance of tenacity lowers that duration individually, stacking on top of each other but only one takes effect at a time. The first instance lowers it by 20% leaving 80%. The 80% becomes a new 100% which is lowered by another 20%. That 80% becomes the new 100% which is lowered by another 30%. By doing this, you can never reach 0% value because there is always something left over.