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Calculation Change Due to Bonus Armor Penetration?

Celeste Benal·11/3/2015, 5:51:35 PM·2 votes·1,026 views

With the new armor pen items coming in season six, it occurred to me that the calculations for armor pen and reduction may be changing. Currently the order of precedence is:

  1. Flat Armor Reduction
  2. Percent Armor Reduction
  3. Percentage Armor Penetration
  4. Flat Armor Penetration

This is easy enough to calculate because until now all items that granted one or more of these stats only effect total armor. But now we have items that only effect bonus armor.

  • Last Whisper: +30% bonus armor pen
  • Mortal Reminder: +40% bonus armor pen
  • Lord Dominik's Regards: +40% bonus armor pen.

How will effective armor be calculated when total armor pen is reliant on the sum of bonus armor and base armor? Will bonus armor have to be calculated first and then total reductions and pens applied? Does this not reduce the effectiveness of armor pen runes and all other forms of total armor pen or reduction? Will this open the door to base armor pen?

Currently, if a champ has 200 bonus armor and 100 base armor (random easy to use numbers for the example), and someone with a 10 flat reduction, 20% reduction, 30% pen, and flat 10 pen comes along, the result is ((300-10) x (1-.2) x (1-.3)-10)=152 armor.

But now someone building both Black Cleaver and Last Whisper has both a total % armor reduction ability and a bonus armor pen ability. Will the total reduction apply first, and then the effective remaining bonus armor then be penetrated, or will the pen on the bonus armor be calculated first and then the total armor reduction?

2 Comments

SCi am I11/15/2015, 8:24:33 AM1 votes

I have that same question.... Wu has his q that will reduce up to 30% armor, and if that focus' the base or is split 15% to bonus and 15% to base armor, then he will do waaaaay more damage with last whisper. But if that 30% targets the opponent's bonus armor first, the last whisper passive is not nearly as effective! THIS NEEDS AN ANSWER!!!

Kaiyn5/24/2016, 3:16:02 PM1 votes

I agree this needs to be answered, If a riot member could answer how penetration works with bonus armour pen being a thing. Currently on the wiki, it says that armor pen and bonus armor pen stack additively as oppose to multiplicitively. That would explain why with darius, when i have E max and lord dom or mortal reminder, my % arm pen according character stats in game, is 70%. If that is the case, that it is additive (25 + 45 = 70%), then my question is why? Because doesnt that make bonus arm pen not bonus. Lets say I have 500 armor 100 base + 400 bonus If its additive, darius' 25% arm pen + 45 bonus arm pen = 70% arm pen Then its simply 70% of 500 is taken away for dmg purposes. But that means, mortal or lord dom is not actually bonus arm pen. and if that 70% is to bonus armor only, so the 400, then darius' E is not arm pen, but rather BONUS arm pen. My thinking is, 25% of 500 = 125, so treated with having 375 armor. Then 45% bonus arm pen to 400 = 180 so in total; 500-125-180 = 195 ???? One thing i noticed that is very key, and this is according to the wiki, so assuming that is correct, is that PENETRATION doesn't actually reduce the armor value for other things, So that bonus arm pen still is applied to 400. (Also according to wiki, bonus arm is reduced or penetrated first, so BC + LW font synergize well. but because pen doesn't change the actually armor value, it doesn't matter if it takes from bonus or base first.) Right now, if a riot member could explain how armor pen works with bonus arm pen in the equation, that would be great. If it is additive, Arm pen + bonus arm pen, the why? Cuz it doesn't make sense to me, although thats what in game stats and the wiki say. If its not additive, then my example is my best guess with how it works. But alas only a riot member knows 100%