How does the new Lethality system work? I have tried reading the patch notes but I don't seem to understand. Can someone simplify it for me?

  • It's armor pen, but it scales with level
    – Aequitas
    Commented Feb 14, 2017 at 12:15

1 Answer 1


Looking at the League of Legend's wikia, you have the following explanation:

Lethality is a new statistic introduced in Season 2017. It grants flat armor penetration using the following formula:

Flat Armor Penetration = LETHALITY × (0.6 + 0.4 × Target's level ÷ 18)

Basically, it works the same as armor penetration, but adding the level of the target as a parameter: the higher the level, the greatest the armor penetration.

There is also an example to understand how the damages are calculated:


Given 30 flat armor reduction and 30% armor reduction, and the target is affected by 10 flat armor penetration and 45% bonus armor penetration,

Target A has 300 armor (100 base and 200 bonus armor).

The 300 is reduced to 270 (90 base and 180 bonus armor) by the 30 armor reduction.

The 270 is reduced to 189 (63 base and 126 bonus armor) by the 30% armor reduction.

The 189 is considered to be 132.3 (63 base and 69.3 bonus armor) by the 45% bonus armor penetration.

The 132.3 is considered to be 122.3 by the 10 armor penetration.

Target A takes damage as if it has 122.3 armor.

Target B has 18 armor.

The 18 is reduced to −2 by the 20 armor reduction.

The −2 is not affected by any further calculations because it is less than 0.

Target B takes damage as if it has −2 armor.

  • so having -2 armor means you actually deal additional damage to the target than you are intended to? Commented Feb 14, 2017 at 12:27
  • 1
    @Luciferangel Exactly. The damage reduction that armor offers is not a linear formula, but the lesser armor the opponent have, the more you deal damage.
    – Ksyqo
    Commented Feb 14, 2017 at 18:34
  • No. You will simply take true damage (armor = 0). If a spell is cast and you have 0 armor after reductions, you take the full spell damage. If you have -2 armor, you take the same damage.
    – Oak
    Commented Feb 14, 2017 at 18:48
  • 1
    @Oak That's not true. You actually do take more damage if you have negative resistances. This was confirmed by Riot somewhere. Armor penetration doesn't lower their armor, but if you have armor reduction and the target's armor is actually equal to -2, they will take additional damage. This can be easily seen on minions by using something to lower their magic resist below zero.
    – mbomb007
    Commented Feb 15, 2017 at 22:58
  • You're wrong. Whenever I can I'll log in LoL to grab some Screenshots. Although if you can prove me wrong, go for it.
    – Oak
    Commented Feb 17, 2017 at 11:22

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