# How is the damage reduction calculated from armor/mr? [duplicate]

For example, if your champion has 200 magic resistance / armor and your enemy has some crazy AP/AD damage that can be dealt with one single spell/attack, say 800 damage at once...

Considering the enemy doesn't have any magic/armor penetration (not even MPen/APen runes), how much damage would your champion receive?

• I don't know much about Leagu but the other answer doesnt seem to cover magic resistance. Maybe I'm mistaken though Jun 6, 2014 at 9:34
• Armor and Magic Resistance use the same formula. Despite the unexpected duplicate post notification, I'm glad that I asked, as I would never find it unless I'm using the "diminishing returns" words. Jun 6, 2014 at 11:49
• Also, another thing to consider, this makes my question a tl;dr version of the other post. So instead of deleting this, I'll leave it in case people don't want the long-story version, but aside from that, it's still really clear. Jun 6, 2014 at 11:51

According to League of Legends wikia, both armor and magic resistance "damage multiplier" is calculated with the following formula (replace mr with armor the same):

if enemy MR is greater or equal to 0 (MR >= 0) calculation is like below;

100 / (MR+100)

which means;

for 100 magic resistance → × 0.5 incoming magic damage (50% reduction)

so for a single spell with magic damage of 800 will deal 400 damage (considering your have no magic penetration).

if enemy MR is less than 0 (MR < 0) calculation is like below;

2 − (100 / (100-MR))

which means;

for −25 magic resistance → × 1.2 incoming magic damage (20% increase)

so for a single spell with magic damage of 800 will deal 960 damage (considering your have no magic penetration).