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Attack damage vs Armor Penetration runes

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Senior Member


There simply isn't any way for those AD runes to come out ahead, except precisely at lvl 1 when your arpen may exceed their armor significantly.

There are however some very special cases where AD scales directly into abilities which are unaffected by ArP. Examples are Akalis Twin Disciplines or Udyrs Tiger Stance-DoT.
AD Runes can be viable choice there to get an early game advantage.

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Senior Member


i buy Armor pen runes

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Attack damage will give higher damage in the early levels on just auto attacks in many situations.

Armor penetration will give similar results.

Armor penetration scales better into the late game, especially if combined with other armor penetration sources such as brutalizer (though both stats do depreciate as the game goes on).

It's just a matter of preference. Do you prefer maxing your early game damage for a slight decrease in late game damage?

Also, some characters such as Udyr will benefit more from attack damage runes more if you're jungling with Tiger Stance, because building magic pen for jungling is pointless and Tiger stance does magic damage while scaling with AD.

Here's are some actual calculations assuming level 30:

First off, for simplicity's sake, everything will be calculated in terms of percent increase.

If you build attack damage marks, you get 8.5 damage. If you build armor penetration runes, you get 15 armor penetration.

I'm gonna use Ezreal as my example. His targets will be Ashe, Shen with armor seals, armor masteries and cloth armor, and Ancient Golem.

Ezreal starts with 50 AD at level 1.

->AD runes:

With 0 items:
8.5 / 50 = 17% increase

With Doran's blade (+10 AD):
8.5 / 60 = 14.2% increase

If your champion has higher base damage, AD marks will be less effective, and more effective if it has less.

->ArP runes:

Percent increase can be calculated as follows:

100 / 100+armor = damage taken as a percent

We'll call the armor the target has without armor pen 'a'
We'll call the armor the target has with armor pen 'b'

[(100 / 100+b) / (100 / 100+a)] – 1

Therefore, [(100+a) / (100+b)] - 1 = damage increase gained from armor penetration as a percent.

Ashe has 12 armor at level 1.

Shen has 22 armor plus gets an additional 19 from runes and masteries and +18 from cloth armor for a total of 59 armor at level 1.

Ancient Golem has 24 armor.

[(100+12) / (100+0)] - 1 = 12%

[(100+59) / (100+44)] – 1 = 10.4%

Ancient Golem:
[(100+24) / (100+9)] – 1 = 13.8%

These calculations don't include quints or masteries, because those change the results and I'm looking to illustrate simply the difference between AD and armor pen marks.

This is also ignoring skills. Some skills scale at less than 1:1 AD, some at more, and some do magic damage instead of physical, so there are many variables to consider, which change depending on your champion.

And this also ignores anything higher than level 1, because you'll collect items as you go and more AD from levelling, which may quickly depreciate the value of AD, depending on what you get.

My opinion: I'm more inclined to use AD runes in jungle and ArP in lane. Efficiency as a jungler dictates so much, so I build for max early efficiency. And many jungle monsters also have less than 15 armor.


Depending on your champion, and whom your target is, one will be better than the other at level 1. There's no real definitive answer for it, though you can't really go wrong with either one as the difference in damage will be small.

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Senior Member


If your build ever contains % Pen, or Flat Redux, there is a good chance that the actual functional value of your Flat Pen will be significantly reduced.

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Senior Member


arpen packs a punch early, and scales better later on.

9 marks will give you a whole 8 damage. A hero like Ashe would go from 53 to 61 damage. a 15% increase at level 1 (assuming you aren't using doran's).

9 deso runes gives you 15 arpen, which should give you 31 total (at level 30). so without them, you only have 16. That's fine at lvl 1 vs very squishee people, but let's assume a 31 armor character. Instead of no bonus EHP, they now have 15% bonus EHP vs physical. This means the arpen would give the same effective bonus to damage.

That's at level 1. As things scale your damage goes up, with many pushing 300ish AD by end game. 8 extra damage is a whole ~3% bonus. The added arpen will be much higher.

Take a 300 dmg character vs a 100 armor character. Assume no additional arpen (which favors straight damage).

Against AD marks, they have 84 armor or they take 54.3 % of damage (45.7% reduction)
Against arpen marks then have 69 armor or they take 59.2 % of damage (40.8% reduction)

AD marks hits for 308*.543 = 167 damage
arpen marks hit for 300*.592 = 177 damage

And now realize that with more arpen this advantage grows even larger.

I even tried AD/per level runes and they come out behind arpen.

There simply isn't any way for those AD runes to come out ahead, except precisely at lvl 1 when your arpen may exceed their armor significantly.

That actually does make perfect sense and I understand now. Thanks for clearing that up for me, I guess I have to throw down my next 3k IP towards switching my AD to ArP runes -.- /sigh

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Senior Member


Side note. AD is going to make early last hitting easier than having 30 arp on creeps with 6 armour.

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Senior Member


Well that was a bit rude, however upon further thinking I realized I hadn't done a sample involving a high atk damage vs low armor

So we will assume again we are using Trynd who has one of the highest base attacks in the game.

At level 18 he has 111.62. Against a Fiddlesticks who has a base of 56 armor at 18. Now we are going to assume the Trynd build is going to involve an Infinity Edge for +80 AD and a Bloodthirster for an average of 80 AD. And a Last Whisper which gives +40 AD and 40% armor pen. So total we have 311.62 damage (Estimate. Obviously you can build into a second bloodthirster and keep max stacks so it could be substantially higher but in a real game you are likely to get 3 or 4 of your items and you will need at least one PD in there)

We will also assume that Fiddlestick's isn't totally ******ed and notices a well built trynd killing everyone so he will get a Guardian Angel for some protection putting him to 119 Armor

So 311.62 damage with either 14.94 ArP (For 9 runes) or 8.55 AD.

Now with a 119 armor -40% armor pen is 71.4 - 14.94 = 56.46 armor. So your effective damage is .6391 with against 311.62 damage is going to be 199.15 damage.

Now the same calculation with AD will look like 119 - 40% armor pen is still 71.4 giving you an effective damage of .5834. Starting now with an AD of 320.17 which means that your damage will be 186.78

So the total change will be about 12.37 which is indeed a pretty valid change. However all of this said, for heroes with AD modifiers that deal magic damage, which you will find is a fairly large number, having AD will help add damage to them while Armor Pen will not.

So again TLDR: Armor Pen scales well against squishies late game if you take a lot of AD items however if you plan to use AD modified magic abilities (Like Katarina's dagger/ult or Tryndamere's Spin attack) you will probably see greater benefit from your AD runes. And if you aren't taking a large amount of AD in items, (Say under the 150 mark) You will probably notice almost no difference between ArP and AD.

Flat armor pen is applied before % armor pen. In your example, the situation with ArP runes on Trynd, the armor he is facing is (119-15)x0.6 = 62.4. The final damage number based on the accurate calculation is 192, which is only 5 more than the 187 from the flat AD page.

At the end of the day, the difference is always fairly small in fights. The real benefit of flat AD is for last hitting. The only time flat ArP is better is if you've stacked a huge amount of AD because the more you stack, the smaller the portion of your final damage is coming from the AD runes. At level 1, 15 AD is 25-30% more damage. With 300 damage, 15 AD is only 2.5%. But if you stack AS more than AD, then flat AD is worth more.