Click to open network menu
Join or Log In
Mobafire logo

Join the leading League of Legends community. Create and share Champion Guides and Builds.

Create an MFN Account






Or

's Forum Avatar

Magic Penetration

Creator: Goregrim May 22, 2011 2:22pm
34 posts - page 1 of 4
1 2 3 4
Goregrim
<Member>
Goregrim's Forum Avatar
Posts:
2
Joined:
May 22nd, 2011
Permalink | Quote | PM | +Rep May 22, 2011 2:22pm | Report
I mainly play AP characters so obviously magic penetration is a big part of my act. In the champion statistics screen (C), it has both a number and a percentage. I was curious if these two are added together, or if the higher of the two is chosen. I have runes for penetration that give me 9.3 currently, but when I get a void staff along with my mastery talent, I have a 49% magic penetration, which seems significantly better than 9.3. It seems like a waste of rune slots if it is simply replaced by item effects.

Also, how does magic penetration calculate with champion magic resistance? For example, if an enemy champion had 63% reduced magic damage and I have 49% penetration, does that mean their resistance only offers 14% reduction, or 32% reduction, or some other equation?
Lugignaf
<Veteran>
Lugignaf's Forum Avatar
Show more awards
Posts:
10968
Joined:
Feb 8th, 2011
Permalink | Quote | PM | +Rep May 22, 2011 2:26pm | Report
You do get both. I can't explain it too well though so, I'm going to wait until one of the higher-ups sees this and they'll hopefully explain more.
Jebus McAzn
<Retired Moderator>
Jebus McAzn's Forum Avatar
Show more awards
Posts:
7017
Joined:
Sep 30th, 2010
Permalink | Quote | PM | +Rep May 22, 2011 3:12pm | Report
You calculate magic resist based on a flat amount of magic resist, which translates to a percentage reduction.

If an enemy has 100 MR, they have 100/200 reduced damage or 50%. An enemy with 200 MR will have 200/300 reduced damage or 67%.

Your enemy champion with 63% reduced damage actually has 170 magic resist (because 170/270=63%).

That 170 magic resist will be reduced by your 49% penetration to 86.7 MR, offering 86.7/186.7=46.4% reduced damage.



Magic penetration is calculated in terms of percentage reduction, flat reduction, flat penetration, and then percentage penetration. Your runes, which provide flat penetration, apply before your Void Staff and masteries, which applies percent penetration. A build which runs full magic penetration marks will have approximately 9 magic penetration. Let's say you have 49% penetration again.


Against a target with 50 MR, you will first penetrate 9 of that MR, lowering it to 41, and then penetrate 49% more, lowering 41 to 20.91, meaning that your enemies will be treated as if they had 20.91 magic resist for your spells only.
Goregrim
<Member>
Goregrim's Forum Avatar
Posts:
2
Joined:
May 22nd, 2011
Permalink | Quote | PM | +Rep May 22, 2011 3:20pm | Report
Wow, thank you very much, that was incredibly detailed and exactly what I needed.
Eihn
<Member>
Eihn's Forum Avatar
Posts:
67
Joined:
May 13th, 2011
Permalink | Quote | PM | +Rep May 22, 2011 4:59pm | Report
nice didnt know all of that
DEWO
<Retired Moderator>
DEWO's Forum Avatar
Show more awards
Posts:
5526
Joined:
Feb 15th, 2010
Permalink | Quote | PM | +Rep May 23, 2011 5:28am | Report
Resist reduction and resist penetration are applied in this order:
1. Percent reduction
2. Flat reduction
3. Flat penetration
4. Percent penetration

They add but they are calculated in this sequence.
Did i help you? Click that +Rep

Thanks to jhoijhoi for the sig!
Lord Rygor
<Member>
Lord Rygor's Forum Avatar
Posts:
10
Joined:
May 17th, 2011
Permalink | Quote | PM | +Rep May 23, 2011 9:58pm | Report
I have a question. Say you have 20 magic penetration from Boots of Sorcery and the enemy have 0 MR items. Your spell says it hits for 100 damage. How much damage would you actually do?

Or rather, do enemies take increased damage if a champion has magic penetration items on and they are not actively raising magic resists?
DEWO
<Retired Moderator>
DEWO's Forum Avatar
Show more awards
Posts:
5526
Joined:
Feb 15th, 2010
Permalink | Quote | PM | +Rep May 24, 2011 5:48am | Report
Penetration cant go on minus values. So with 0MR you will deal 100 damage.
But
flat reduction can get your target to minus values for bonus damage (correct me here if i am wrong)

In your maths
If your target has 20MR and you have 20Mpen you will deal 100 damage
If your target has 0MR and you have 2834592837592875928Mpen you will deal 100 damage.
Did i help you? Click that +Rep

Thanks to jhoijhoi for the sig!
Lord Rygor
<Member>
Lord Rygor's Forum Avatar
Posts:
10
Joined:
May 17th, 2011
Permalink | Quote | PM | +Rep May 24, 2011 7:09am | Report
Dang, I may need to re-evaluate the way I build my AP characters then. I tend to go all out on magic pen because I thought it did extra damage if they didn't stack MR! Thanks for this.
TheJohn
<Editor>
TheJohn's Forum Avatar
Posts:
2138
Joined:
Jan 25th, 2011
Permalink | Quote | PM | +Rep May 24, 2011 1:46pm | Report
See if I understood it:

Flat: It's MR-MagicPen/(MR-MagicPen)+100, then I find a %.
%: It's like the flat, but already reduces the %, not the flat.

And

The enemy has 100 MR, so the magic dmg taken is reduced by 50%.
I have 50 MagicPen, so I can "pass" by 33% of his MR.
That means that I have 33% MagicPen? And the damage reduce will decresease to 17%?

It's better to get flat or % MagicPen?
1 2 3 4

You need to log in before commenting.

League of Legends Champions:

Teamfight Tactics Guide