Quote:

**EroticBadass**:

Thank you for the math, I have always wondered which was better.

I don't actually have crit damage b/c the only carry I use is tristana and crit damage is very situational. But I do have crit chance on red/quint which is +12% and translates to 20% crit chance at level 1.

Need to know how crit chance compares to armor pen before I go off wasting around 7000 IP. I know with crit chance I still have problems with armor stacking foes early on, but I also have a great advantage against squishies early on. Seeing as they like to stick around and take some hits and next thing they know they're hit hard.

Maybe an equation that situates damage for 5 hits and 10 hits and seeing if the burst from the critical is diluted by the steady increase of damage from the armor pen runes.

edit:

oh and for the guys still questioning this, armor can go to the negatives and you would use the same equation that the OP is using

Negative, Armor Penetration cannot lower below zero. Armor reduction (abilities, Black Cleaver, Stark's Fervor), which applies before armor pen, can reduce below zero.

Also, armor pen always does more damage per attack than Crit Chance does. The only reasons to use crit chance would be:

1) Abilities that trigger off of crit, such as Tryndamere's Spinning Slash and Bloodlust. More crit chance = more crits = more triggers of these abilities.

2) Burst damage abilities that can crit, such as Pirate's Parrrley. Though Armor Penetration might give more average damage per hit, the sheer output of a critical strike on Parrrley makes it potentially worthwhile to increase its crit chance. Armor pen improves the damage of a non-crit 500-base parrrley by ~40 against a target with 80 armor (fairly standard for level 18), but a critical without the armor pen does over 250 more. Considering you can parrrley only once every few seconds, it is arguably better to maximize the chance of having a massive damage parrrley than it is to boost the damage on each regular parrrley.