Formulas for calculating physical penetration in League of Legends

Before we look at the formula for calculating penetration, it is important to note that when dealing damage to an enemy, armor reduction and penetration are taken into account in strict sequence:

Quantitative reduction in armor

Armor reduction %

Armor penetration %


Important: base armor and bonus armor are calculated separately.


Now let’s look at each of these points separately.


Quantitative armor reduction:

Example: your champion has 30 armor reduction, while the enemy has 20 base defense and 40 bonus. In such a situation, the enemy’s base armor will be reduced by 10, and the bonus by 20, and as a result the enemy will have 30 points of defense. Reducing “quantitative” armor can reduce the target’s armor below zero. For example, if the enemy has 10 defense, and our champion has 25 penetration, then the enemy will have -15 defense and bonus damage will hit him.

Formulas for calculating physical penetration in League of Legends

Armor reduction percentage:

From the name it becomes clear that in this case the target’s armor is simply reduced as a percentage. For example, if you reduce an enemy’s armor by 20%, and he currently has 30 armor, his armor becomes 24. Percentage armor reduction is very effective against enemies with high armor. For example, if you reduce the target’s armor by 40%, and the enemy has 200 units of physical defense, then you will reduce this indicator by 80. In other words, the more armor the target has, the more effectively this indicator works. The percentage reduction in armor works simultaneously for both base and bonus defense, but does not work if the target’s defense has become 0.


Percentage armor penetration:

Although the name of this indicator is different from the previous one, the principle of its operation is exactly the same. The only difference is that the armor reduction is triggered first, and then penetration is calculated.



Lethality is calculated using the formula (0.6 + 0.4 × Target Level ÷ 18). From the formula it becomes clear that lethality will work more effectively as the enemy level increases, but still at least 40% of the target’s defense will be cut off. The maximum effect is achieved at enemy level 18. If, for example, your champion has 20 lethality and the enemy has 30 defense, then the damage will be calculated as if the enemy had 10 defense.


For magical penetration, damage is calculated in approximately the same way, but there are no problems with lethality.