Talk:List of runes/@comment-192.223.163.6-20120328205832/@comment-5490997-20120923161950

If you know how effective HP works you'd see he's right.

The theory of effective HP is that MR and Armor add a % of HP to your base HP. As a matter of fact every 1 point of MR/Armor adds 1% effective HP (as seen on the same page you linked). The reason to work with effective HP is because it allows you to easily calculate how many attacks it will take to kill someone (and show you what is more effective that way).

Now ArPen and MPen basically "removes" (some) of that armor/mres, so it effectively reduces a champion's effective HP. It also means that when calculating with effective HP Mpen plays no role in how much damage a spell deals.

Let's take your example, but do the math in effective HP. I'll give the target 2K HP since that's easy to work with.

2K HP and 30 Mres means that target has 2000+30%=2600 effective HP.

Example A: You have 20 AP, so your spell deals 320 damage (300 base + 20 AP). That means you need to do 2600/320=8.125 attacks to kill that target.

Example B: You have 20 Mpen, so your spell deal 300 damage. Because you have Mpen you reduce your target's effective HP by 20% and it's like his Mres only gives him 10% more HP. 2000+10%=2200. 2200/300=7.33 attacks needed to kill the target. Which is right if you do 2000/272.7=7.33.

7.33 is less than 8.125 so the Mpen is more effective in this case, just like you said. As you can see however is that you basically gain 20 damage per cast with AP, while you reduce someone's effective HP with Mpen. AP adds effective damage, while Mpen reduces the amount of effective HP the target has. That's probably what the anon was trying to say.

With only 100 base damage example A would need 21.66 attacks and in example B 22 attacks. So AP is slightly better, but because both round off to 22 attacks there is actually no difference.

Hopefully that clears some stuff up about effective HP for you guys. Instead of calculating how much damage each attack does and then dividing a target's HP by that to see how many attacks it would take, it is far easier to calculate how much HP a target really has (effective HP) and just divide it by the damage you deal.

btw, the 250.8 you calculated in example A is wrong. If I type in that same calculation I get 246.15 and 2000/246.15=8.125. Which would match with my effective HP calculation.