I did some math recently and received these results:

Quote:

__LvL 6 Caitlyn Shooting, 66 Armor targe__t

*Modified(8 AD Reds, 1 ARP Red, 2 AD Quint, 1 ARP Quint):*

Base damage with runes and masteries: 65 + (3 + 3 from masteries) + (12 from runes) = 83.

Now we calculate the total armor she is going to deal damage against: (66 - 11 from runes and masteries) - [.1*(66 - 11)] from masteries. Caitlyn's damage will be calculated against 49.5 armor.

49.5 armor reduces 49.5/(100+49.5) damage. Caitlyn's 83 AD will be reduced by 33.11%

So 83 - (83*.3311) = __55.5187 total damage.__

*Full ARP:*

Base damage with runes and masteries: 65 + (3 + 3 from masteries) = 71.

Now we calculate the total armor she is going to deal damage against: (66 - 31 from runes and masteries) - [.1*(66 - 31)] from masteries. Caitlyn's damage will be calculated against 31.5 armor.

31.5 armor reduces 31.5/(100+31.5) damage. Caitlyn's 71 AD will be reduced by 23.954%

So 71 - (71*.23954) = __54 total damage.__

*Full AD:*

Base damage with runes and masteries: 65 + (3 + 3 from masteries) + (15.3 from runes) = 86.3.

Now we calculate the total armor she is going to deal damage against: (66 - 6 from masteries) - [.1*(66 - 6)] from masteries. Caitlyn's damage will be calculated against 54 armor.

54 armor reduces 54/(100+54) damage. Caitlyn's 86.3 AD will be reduced by 35.06%

So 86 - (86*.3506) = __55.8484 total damage.__

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__LvL 12 Caitlyn Shooting, 80 Armor target__

*Modified(8 AD Reds, 1 ARP Red, 2 AD Quint, 1 ARP Quint):*

Base damage with runes and masteries: 83 + (6 + 3 from masteries) + (12 from runes) = 104.

Now we calculate the total armor she is going to deal damage against: (80 - 11 from runes and masteries) - [.1*(80 - 11)] from masteries. Caitlyn's damage will be calculated against 62.1 armor.

62.1 armor reduces 62.1/(100+62.1) damage. Caitlyn's 104 AD will be reduced by 38.3096%

So 104 - (104*.38309) = __64.15864 total damage.__

*Full ArP:*

Base damage with runes and masteries: 83 + (6 + 3 from masteries) = 92.

Now we calculate the total armor she is going to deal damage against: (80 - 31 from runes and masteries) - [.1*(80 - 31)] from masteries. Caitlyn's damage will be calculated against 44.1 armor.

44.1 armor reduces 44.1/(100+44.1) damage. Caitlyn's 92 AD will be reduced by 30.603%

So 92 - (92*.30603) = __63.84524 total damage.__

*Full AD:*

Base damage with runes and masteries: 83 + (6 + 3 from masteries) + (15.3 from runes) = 107.3.

Now we calculate the total armor she is going to deal damage against: (80 - 6 from masteries) - [.1*(80 - 6)] from masteries. Caitlyn's damage will be calculated against 66.6 armor.

66.6 armor reduces 66.6/(100+66.6) damage. Caitlyn's 107.3 AD will be reduced by 39.9759%

So 107 - (107*.3997599) = **64.2256907 total damage.**

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__LvL 18 Caitlyn Shooting, 200 Armor target__

*Modified(8 AD Reds, 1 ARP Red, 2 AD Quint, 1 ARP Quint):*

Base damage with runes and masteries: 101 + (9 + 3 from masteries) + (12 from runes) = 125.

Now we calculate the total armor she is going to deal damage against: (200 - 11 from runes and masteries) - [.1*(200 - 11)] from masteries. Caitlyn's damage will be calculated against 170.1 armor.

170.1 armor reduces 170.1/(100+170.1) damage. Caitlyn's 125 AD will be reduced by 62.9766%

So 125 - (125*.629766) = __46.279 total damage.__

*Full ArP:*

Base damage with runes and masteries: 101 + (9 + 3 from masteries) = 113.

Now we calculate the total armor she is going to deal damage against: (200 - 31 from runes and masteries) - [.1*(200 - 31)] from masteries. Caitlyn's damage will be calculated against 152.1 armor.

152.1 armor reduces 152.1/(100+152.1) damage. Caitlyn's 113 AD will be reduced by 60.3332%

So 113 - (113*.603332) = __44.823484 total damage.__

*Full AD:*

Base damage with runes and masteries: 101 + (9 + 3 from masteries) + (15.3 from runes) = 128.3.

Now we calculate the total armor she is going to deal damage against: (200 - 6 from masteries) - [.1*(200 - 6)] from masteries. Caitlyn's damage will be calculated against 174.6 armor.

174.6 armor reduces 174.6/(100+174.6) damage. Caitlyn's 128.3 AD will be reduced by 63.58339%

So 128 - (128*.6358339) = __46.61326 total damage.__

I hope this helped you. My results were calculated theoretically, you can apply the same test for your champion and your desired amount of damage.

As you can see for low-medium amount of damage AD and ArP runes give nearly the same damage output(0-1 difference). As your damage increases the Armor Penetration start taking effect and then you start dealing some minor bonus damage, but this is in late(mid) game and late game when you start dealing >250 damage.

**The best advantage AD Runes have over ArP is that you will have 10-15 bonus damage early game and you can last hit the creeps with better efficiency**. They really help me because I am from Europe and play here on NA, I have >200 ping :/

Here is a link explaining the pros and cons of AD/ArP in early/mid/late game.

http://rog.clgaming.net/blogs/a-different-view/5913-debunked-are-arpen-runes-better-than-ad-runes-redux