I have seen at least 3 threads lately about how Armor/MR is best used in moderation, as they have "diminishing return".

Until last night, I thought the same thing. I always bought a little armor and MR on non-tanks, seeing as it was so much more important.

But now think of it this way: If I have 100 armor, that means I have 50% reduction. This means that if I have 1000 health and my opponent has 100 AD, it will take 20 shots to kill me. No armor means 10 shots. 300 armor means 30 shots.

Of course, for anyone past 6th grade math, this should seem counter-intuitive. If every point I get gives me .98% (approximately) of the value of my last one, then it **is** diminishing return.

The only way to understand this is by first understanding what health is. Health is one of the two factors that go into your DC (Damage Capacity). The other one is your armor. So therefore, your armor isn't just protecting your health. It's also protecting... your armor.

So because of this, your armor protects itself, and therefore has no diminishing return. Because as you stack armor, you are giving better protection to your DC, and having linearly more durability.

For those of you who like it in math form, here's the equation:

a = armor, d = damage (of opponent), h = health, and y = hits required to kill you.

y=h/(100/(100+a))*d

Try a few different a's. It's linear.

So this should clear things up. Armor/MR are linear, and the only difference between them and health is "max health %" spells, which favor Armor/MR, and true damage spells, which favor health.

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