### Let's talk Armor

AhrimanHJ

Senior Member

Anyone with any knowledge of math should be able to grasp this intuitively, but for those who for some reason just don't get it, let us talk about the mechanics of armor and magic resist.

The damage reduction formula is this Armor/Resist divided by (Armor/Resist+100), the / indicates or, because it depends on whether we are talking physical or magical damage. I want to go over some numbers with you that you might find useful.

50 armor: achievable on bruisers early game, and definitely a goal to shoot for with most jungling builds. will reduce all physical damage by 33%.

100 armor: a 50% reduction for physical damage. Also fairly easy to aim for, and I find it a convenient benchmark.

150 armor: this is where the damage reduction becomes not worth the cost. It takes about 150 armor to block 60% of the damage, but to block 66%, you need to get 50 more armor. At this point it is more beneficia to buy health, unless there are special circumstances involved. I never expect to get more than about 66% reduction per game due to many factors.

For MR, these magic figures are about the same. However, when building for MR, due to the nature of casters and items, one needs to think a little differently.

Now, with regards to defenses, one has to think about the enemy use of armor penetration.
For Armor, that's 21 if we account for optimal runes and masteries, 30 if they take the quints. Starks Fervor, Youmuu's Ghostblade add 20 armor pen, and Sword of the Divine adds 30. Last Whisper penetrates 40% of your armor. The Black Cleaver can reduce your armor by up to 45 over three shots. Understand that if an enemy has flat penetration and a last whisper, the last whisper's reduction comes last. Meaning if you have 100 armor, and they have 20 pen and a whisper, you will lose 100-20=80, 80*(1-40%)=44 armor. Starks Fervor and Black Cleaver offer reduction, which is calculated first, and can reduce armor below 0 (penetration stacks last and cannot push armor below 0)
Magic Penetration has similar items, the Abyssal Scepter offers 20 flat reduction,the Haunting guise offers 20 penetration, and the Sorceror's shoes offer another 20. Void staff is another 40% penetration. Runes for magic pen give about 9, and the mastery for it gives 15% penetration.

So how do we build around this fact? Well, we have to first set our sights on our magic numbers. For me, I tend to go for 100 for situations and off tanks, and 150 for tanks.
For physical defense, I tend to go for 150+21+20+20= around 215-220 armor. That way I get over 150 armor if they get armor pen, and still have over 150 in case they buy last whispers. For a tanky champion, that usually means buying about 150-180 in terms of bonus armor items; for situational things like vs a team of all ad with tryndamere, I just buy thornmail and call it a day.

Magic is a little bit trickier, but follows the same principles. Due to the mastery, mages have innate 15% pen, with the 40% void staff(which is rainly bought) that means over half your magic resist is bypassed. But not to worry. Due to the bursty nature of casters, a banshees veil goes a long way, meaning that settling for about 100 or so resistance is enough. Merc Treads + Banshees Veil + assorted runes puts me at about 125 or so late game. If they buy a lot of penetration, just build as you go along. For dps, I take Wit's End and possibly Hexdrinker as well. for the extra 65 resist. If I am playing a caster, and I am afraid of magic damage, I build Abyssal Scepter as my core offensive item. But the team comp screen shows a lot of magic damage, the veil and the boots are definitely a must have. Taking 50% reduced damage is a huge deal.

Now I have talked about the calculations for building defensively; however, offensive needs must be discussed as well.
Most champions start with low armor and higher mr. Armor growth is higher. For default champions, mr has 2 tiers the 30 at lv 18 tier and the 52 at lv 18 tier. Armor has much more variation, but in general, casters have about 40-50 late game and tanky dps has about 80-90. This is not counting bonuses, runes, or items or masteries.
Now, this immediately tells you that Last Whisper is more often a better item than void staff. Whisper alone against a team with no armor will give more penetration than a void staff against teams that don't build mr. Of course both are situational, just that Whisper is less situational, and in some ways, worth building for its damage alone.
Armor runes aren't necessarily taken unless one jungles, but mr runes are common, so they warrant a +13 for our penetration calculation. Also, the masteries in defense give +6 in each, but again, usually only tanky melee dps take those.

Armor is a bit trickier, but understand that armor reduction and penetration help many champions. For mid game, the runes and masteries are very good, and a Brutalizer will increase your armor penetration to about 36, which, given how early in the game you can aquire it, will drastically increase your damage. Armor doesn't have a general case, the rule is, if the person whom you wish to target gets over 40 bonus armor, you get the last whisper. Last Whisper + Madreds Bloodrazor is a devastating combination of items. Youmuu's Ghostblade is good for similar reasons. Starks Fervor is usually suboptimal on a melee carry, unless you really love it with a passion, ask a team mate to get it, so you can get higher items like infinity edge or the like. With armor pen, the key is to try and reduce the enemy's armor to around 50 or so, 33% reduction is not nearly enough to stop a farmed physical carry.

Skills: Many skills can augment armor and magic resist. I won't list them all, but you can find them on wikipedia. I will list notable ones. You usually won't be able to build around most of these, just be aware.

Soraka's Passive and her Q
FiddleSticks Passive
Jarvan's Q reduces armor by %(this procs before flat reduction or any penetration)
Jarvan's Flag gives up to 26 armor to allies and 52 armor to himself.
Taric's Aura +60 armor to self, 30 to teammates
Corki's E can take out about 50 armor, I always buy cleaver for him.

In Conclusion:
I hope this guild will help you plan your builds better, and I hope I have explained the mechanis of the defensive stats. I know that LoL is so situational that you build differently in every game, but I believe that this set of guidlines will help you optimize the performance of your champions both defensively and offensively. I know I cannot address all situations and all items, but I hope that I can help the community learn to build against common circumstances.

KaiXiang

Member

I'd like to point out that the Magic Pen Mastery + Void staff will only equal to 49% Penetration.

15% + ( 40% * 85%) = 15% + 34% = 49%

AhrimanHJ

Senior Member

oh right sorry, I thought it just stacked onto a flat number. nevertheless, 49% is close to half.

Fluffy1

Senior Member

pretty much you aim for the 50% reduction, buyig more resistance is they have pen. casters are pretty weak right now cause 200 MR cannot be countered and 200 MR is far cheaper than magic pen.

once someone has 200 MR best they can do is get it to around 90-100, still half damage making a casters burst worthless and they are out of the fight for 7-10 sec.

armour on the otherhand isnt soo bad as not only is the damage sustained enough to be noticable but there are many dps items that change damage type to magical.

the pen system needs an overhaul.

Nornamor

Member

lulz, sry.... kinda stopped reading at the 150 armor part..

you know that the mitigation difference between 33% and 50% is equally big as the mitigation difference between 50% and 66%? Both raises your mitigation level by 33%.

If you dont understand that let me show an more understandable example:

can you see that the mitigation difference between 0% and 50% is equally big as the mitigation difference between 98% and 99%? Both raises your mitigation level by 50%, think about it for a second why this is true.

--> There is no "soft"-cap to armor, if you don't understand the formula why do you use it?

300armor is twice as good mitigation as 150 armor, even though the reduction is 75% for 300 and 60% for 150

AhrimanHJ

Senior Member

I see the law of diminishing returns. Going from 50 armor to 100 armor mitigates 17% more of the total damage. Or, increasing the amout of mitigation by 50% about. However, it takes 100 more armor to reduce the achieve a similar increase in defense. I am merely saying that after a while, it takes too much armor for too little gain.

I see the casters dilemma, because I play a lot of kassadin. After you start seeing bubbles on everyone you just kinda sigh.

recursionGeneral

Junior Member

One way to look at it is that 100 armor makes you 100% of your health harder to kill by physical damage and the same with mr for magic damage. For example if you had 1000 hp and 100 armor, you have the equivalent of 2000 physical hp. If you have 1000hp and 200 armor, you have the equivalent of 3000 physical hp. The formula is hp + hp * (armor|mr / 100) -- the "/" is for division and "|" is for or. This does not include armor or magic penetration and it needs to be calculated separately for armor and mr. For this reason, health can be advantageous as it increases both. For example if you have 1000 hp, 100 mr, and 50 armor, you have the equivalent of 2000 magic hp and 1500 physical hp. If you have 2000 hp, 100 mr, and 50 armor you have the equivalent of 4000 magic hp and 3000 physical hp.