# Magic penetration

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Magic penetration is a champion statistic which allows the magic damage done from their abilities, enhanced attacks, etc. to ignore some or all of a target's magic resistance.

Note: Magic Penetration cannot affect enemy magic resistance beyond 0 to deal bonus damage.

Magic resistance reduction is the effect of some items and champion abilities that temporarily reduces the magic resistance of one or more targets. This allows allies to benefit from the reduction of magic resistance. This can reduce magic resistance below 0, resulting in bonus damage (see Magic resistance).

## Order of calculations

Magic penetration and magic resistance reduction work exactly like armor penetration and armor reduction.

Magic penetration and magic resistance reduction are considered on the target champion in the following order:[1]

1. Magic resistance reduction, flat.
2. Magic resistance reduction, percentage.
3. Magic penetration, percentage.
4. Magic penetration, flat.

## Flat magic resistance reduction

Flat magic resistance reduction stacks additively.

Example: 20 magic resistance reduction reduces the target's magic resistance by 20, so a target with 30 magic resistance will be reduced to 10 magic resistance. (30 − 20 = 10)

Flat magic resistance reduction can reduce a target's magic resistance below zero. For example, if an enemy with 10 magic resistance has their magic resistance reduced by 25, the enemy will have −15 magic resistance.

## Percentage magic resistance reduction

The target's magic resistance is multiplied by a percentage (100% − the listed reduction). Percentage magic resistance reduction stacks multiplicatively and is ignored if the target's magic resistance is 0 or less.

Example: 20% magic resistance reduction multiplies the target's magic resistance to 80%, so a target with 30 magic resistance will be reduced to 24 magic resist. (30 × 0.8 = 24)

Percentage magic resistance reduction makes a bigger difference on targets with higher magic resistance. For instance, with 40% magic resistance reduction, a target with 200 magic resistance will lose 80 while a target with only 50 magic resistance will lose 20.

## Percentage magic penetration

The target's magic resistance is treated as being multiplied by a percentage for purposes of damage calculation (100% − the listed penetration). Percentage magic penetration stacks multiplicatively and is ignored if the target's magic resistance is 0 or less.

Example: 20% magic penetration causes the target to take damage as if its magic resistance was multiplied by 80%, so a target with 30 magic resistance will be treated as though it had 24 for purposes of damage calculation (the target's actual magic resistance value will not change, however).

Because the target's actual magic resistance value does not change, anything else depending on that value also doesn't change (e.g. ).

Percentage magic penetration makes a bigger difference on targets with higher magic resistance. For instance, with 40% magic penetration, a target with 200 magic resistance will be considered as having 80 less while a target with only 50 magic resistance will be considered as having 20 less.

## Flat magic penetration

The target's magic resist is treated as being reduced by an amount for purposes of damage calculation, but cannot be reduced below 0. Flat magic penetration stacks additively.

Example: 20 magic penetration causes the target to take damage as if its magic resistance was 20 less, so a target with 30 magic resistance will be treated as though it had 10 for purposes of damage calculation (the target's actual magic resistance value will not change, however).

Because the target's actual magic resistance value does not change, anything else depending on that value also doesn't change.

## Examples

Given 20 flat magic resistance reduction and 30% magic resistance reduction, and the target is affected by 10 flat magic penetration and 40% magic penetration,

• Target A has 80 magic resistance.
• The 80 is reduced to 60 by the 20 magic resistance reduction.
• The 60 is reduced to 42 by the 30% magic resistance reduction.
• The 42 is considered to be 27.3 by the 35% magic resistance penetration.
• The 27.3 is considered to be 17.3 by the 10 magic resistance penetration.
Target A takes damage as if it has 17.3 magic resistance.
• Target B has 18 magic resistance.
• The 18 is reduced to −2 by the 20 magic resistance reduction.
• The −2 is not affected by any further calculations because it is less than 0.
• Target B takes damage as if it has −2 magic resistance.

Graph of % increase in damage of mpen vs no mpen, at up to 300 MR:

## Increasing magic penetration

### Items

• : Unique Passive – Eyes of Pain: +15 magic penetration
. +200 health, +25 ability power. 1600
• : Unique Passive – Eyes of Pain: +15 magic penetration
. +300 health, +80 ability power. Unique Passive: Dealing spell damage applies a damage-over-time effect for 3 seconds that deal 2% of target's current health bonus magic damage per second. This bonus damage is doubled against movement-impared units and capped at 100 damage per second vs. monsters. 3200
• : +15 magic penetration
. Unique passive – Enhanced Movement: +45 movement speed. 1100
• : Unique Passive: Magic damage ignores 35% of the target's magic resist (applies before magic penetration)
. +80 ability power. 2650

### Masteries

Note: Only the magic penetration bonus effect of these abilities is shown here. To read more information on each of these abilities, follow the link on each of them.

• grants 1.4 / 2.8 / 4.2 / 5.6 / 7% magic penetration.
• grants 0.6 + (0.06 × level) / 1.2 + (0.12 × level) / 1.8 + (0.18 × level) / 2.4 + (0.24 × level) / 3 + (0.3 × level) magic penetration.

### Runes

Name Type Tier 1 (Lesser) Tier 2 (Normal) Tier 3 (Greater)
Magic Penetration Mark

0.49

N/A

0.68

1

0.87

410

Seal X X X
Glyph

X X 0.63

410

Quintessence

1.12

N/A

1.56

1

2.01

1025

Hybrid Penetration Mark

X X 0.62 magic penetration
0.9 armor penetration

820

Seal X X X
Glyph X X X
Quintessence

X X 1.4 magic penetration
1.79 armor penetration

2050

## Reducing magic resistance

### Items

• reduces the magic resistance of nearby enemy champions by 10 - 25 (based on level) (700 range).
• basic attacks reduce the target's magic resistance by 5 on hit, stacking up 5 times.

### Champion abilities

Percentage reduction:

• reduces the magic resistance of the target by 20 / 22 / 24 / 26 / 28% for 4 seconds.
• empowers his next auto attack to reduce the enemy's magic resistance by 10 / 15 / 20 / 25% for 5 seconds.
• reduces the magic resistance of all targets affected by 15% for 5 seconds.
• allows her autoattacks against enemy champions reduces their magic resistance by 3% for 5 seconds. This debuff stacks up to 5 times.
• reduces the magic resistance of his target by 20% and gains for the same amount. This amount is doubled over the next 4 seconds. The magic resistance reduction lasts for another 4 seconds after the drain completes.

Flat reduction:

• passively makes his autoattacks reduce the magic resistance of enemies hit by 15 / 20 / 25 for 3 seconds.

## Notes

• Magic penetration is a very valuable stat for casters. There are few sources for it and so Magic Penetration marks are very popular runes.
• Since percentage penetration is applied before flat penetration, it is highly recommended to combine both statistics.
• Commonly only one of or is built depending on how much magic resistance the enemy team is using.
• Magic penetration not only affects all champion abilities that deal magic damage, but also affects magic damage items.
• The actives on items like benefit from magic penetration as well.
• Turrets are also subjected to magic penetration effects.

## Trivia

• The biggest amount of magic penetration any champion can obtain at level 18 is:
• 49.53 flat + 39.55% magic penetration with
• 57.93 flat + 35% magic penetration with .
• Runes: +19.53 magic penetration
• Masteries:
• Option 1: (+7% magic penetration)
• Option 2: (+8.4 magic penetration)
• Items: +30 magic penetration and +35% magic penetration
• 1 or (+15 magic penetration)
• 1 (+15 magic penetration)
• 1 (+35% magic penetration)
Relevant mathematics
• Magic penetration with Option 1:
• Items =  +  +  = 30 flat + 35% magic penetration
• Runes =  +  +  = 19.53 magic penetration
• Masteries =  = 7% magic penetration
• Flat Magic Penetration = 30 + 19.53 = 49.53 magic penetration
• Percent Magic Penetration = (2 − (2 − 1.35) × (2 − 1.07)) = 39.55% magic penetration
• Magic penetration with Option 2:
• Items =  +  +  = 30 flat + 35% magic penetration
• Runes =  +  +  = 19.53 magic penetration
• Masteries =  = 8.4 magic penetration
• Magic Penetration = 30 + 19.53 + 8.4 + 35% = 57.93 flat + 35% magic penetration