*Lethality*redirects here. For the 2013 Mastery, see Lethality.

**Armor penetration** is a champion statistic that reduces the effectiveness of a target's armor.

As an example, 10% armor penetration causes a target to take damage as though they had 10% less armor, or, equally, 10% armor penetration is equivalent to fighting a target with 10% less armor. The difference between armor penetration and armor reduction is that armor reduction can reduce armor below zero and affects any source of physical damage to a target. The effects of armor penetration, on the other hand, are ignored once the target's effective armor drops below 0, and only the source of the armor penetration reaps the benefits.

**Lethality** is a champion statistic introduced in season 2017 that is converted to flat armor penetration at a rate that increases based on your level, see formula below^{[1]}.

All champions have 0 base armor penetration, but it can be increased with items, runes, and some champion abilities.

## Order of calculations

When attacking, armor penetration and armor reduction are considered in the following order: ^{[2]}

- Armor reduction, flat
- Armor reduction, percentage
- Armor penetration, percentage
- Lethality

Note: **Base** armor and **bonus** armor are calculated separately.

## Flat armor reduction

The target's armor is reduced by an amount. Flat armor reduction from different sources stacks additively and is distributed proportionally between base armor and bonus armor.

*Example: 30 armor reduction against a 20 base armor and 40 bonus armor target will reduce base armor by 10 and bonus armor by 20, so the target will be reduced to 30 armor ((20 − 10)*+*(40 − 20) = 30*)*.*

Flat armor reduction can reduce a target's armor below zero. For example, if an enemy with 10 armor has their armor reduced by 25, the enemy will have −15 armor.

## Percentage armor reduction

The target's armor is multiplied by a percentage (100% − the listed reduction). Applies to both base and bonus armor. Percentage armor reduction stacks multiplicatively and is ignored if the target's armor is 0 or less.

*Example: 30% armor reduction multiplies the target's armor to 70%, so a target with 20 base armor and 40 bonus armor will be reduced to 42 armor ((20 × 0.7*) + (*40 × 0.7*)*= 42).*

Percentage armor reduction makes a bigger difference on targets with higher armor. For instance, with 40% armor reduction, a target with 200 armor will lose 80 while a target with only 50 armor will lose 20.

## Percentage armor penetration

The target's armor is treated as being multiplied by a percentage for purposes of damage calculation (100% − the listed penetration). Percentage armor penetration stacks multiplicatively and is ignored if the target's armor is 0 or less.

*Example: 30% armor penetration causes the target to take damage as if its armor was multiplied by 70%, so a target with*20 base armor and 40 bonus armor will be treated as though it had 42 for purposes of damage*(the target's actual armor value will not change, however)*(*(20 × 0.7*)*+*(40 × 0.7 = 42).

Because the target's actual armor value does not change, anything else depending on that value also doesn't change (e.g.

).Percentage armor penetration makes a bigger difference on targets with higher armor. For instance, with 40% armor penetration, a target with 200 armor will be considered as having 80 less while a target with only 50 armor will be considered as having 20 less.

### Percentage bonus armor penetration

Percentage armor penetration that applies only to **bonus** armor.

*Example: 30% bonus armor penetration multiplies the target's bonus armor to 70% without affecting base armor, so a target with 20 base armor and 40 bonus armor*will be treated as though it had 48 for purposes of damage calculation (the target's actual armor value will not change, however).*(20*+ (*40 × 0.7*)*= 48).*- If the player has multiple sources of percentage bonus penetration, they stack multiplicatively:
*Example: 10% armor penetration and 30% bonus armor penetration*.*(20 × 0.9))*+ (*40 × 0.7 × 0.9)*)*= 43.2).*

Because the target's actual armor value does not change, anything else depending on that value also doesn't change (e.g.

).Percentage bonus armor penetration makes a big difference on targets who build armor items, but will do nothing against base armor.

## Lethality

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

**Flat Armor Penetration**= Lethality × (0.6 + 0.4 × level ÷ 18)

The target's armor is treated as being reduced by an amount for purposes of damage calculation, but cannot be reduced below 0. Flat armor penetration stacks additively.

*Example 1: 20 lethality causes a target(level 18) to take damage as if its armor was 20 less, so a target with 30 armor will be treated as though it had 10 for purposes of damage calculation (the target's actual armor value will not change, however).*

Because the target's actual armor value does not change, anything else depending on that value also doesn't change (e.g.

).### Examples

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 −12 by the 30 armor reduction.
- The −12 is not affected by any further calculations because it is less than 0.
- Target B takes damage as if it has −12 armor.

## Increasing lethality

### Items

### Runes

## Increasing armor penetration

### Items

### Champion abilities

## Reducing armor

### Items

### Champion abilities

- Percentage Reduction

- Flat Reduction

## Notes

- Armor penetration is a very valuable stat for physical damage dealing champions. There are few sources for it, so armor penetration Marks and Quintessences are very popular runes.
- Armor penetration benefits all sources of physical damage including all champion abilities that deal physical damage.
- For example, will benefit from armor penetration as it deals physical damage, however his will not benefit from armor penetration as it deals magical damage.
- The items that deal on-hit physical damage: , , , , and , will also benefit from armor penetration.

- Turrets are also subjected to armor penetration effects.

## Trivia

- The biggest amount of
*lethality*any champion can obtain is**74**: **Runes:****Items:**- 1
- 1
- 1
- 1

**Relevant mathematics:****Items**= + + + = 64 lethality**Runes**= = 10 lethality

- Total = 64 + 10 =
**74**lethality

## References

Offensive | 15px Ability power · Attack damage · 15px Attack speed · 15px Critical strike chance · 15px Critical strike damage · 15px Armor penetration · 15px Magic penetration · 15px Life steal · 15px Spell vamp · 15px True damage |
---|---|

Defensive | Heal and shield power · Health · 15px Health regeneration · Armor · 15px Magic resistance · Tenacity · Slow resist |

Utility | Cooldown reduction · 15px Energy · 15px Energy regeneration · 15px Mana · 15px Mana regeneration |

Other | 15px Experience · 15px Gold generation · Movement speed · Range |