Ability power

Ability power (or AP) is a stat that increases the effectiveness of most champions' abilities. Abilities in League of Legends that are affected by ability power have an ability power ratio. This ratio determines how much a particular ability will benefit from a champion's total ability power, whether through increased damage, healing, and other numerical values. Ability power stacks additively.

Calculations To calculate the bonus to a numerical value in an ability, the formula is
 * Bonus = AP &times; AP ratio.

For example, if a damage spell has an ability power ratio of 0.25, every 4 points of ability power will increase the damage of this ability by 1. Abilities that are affected by ability power are identifiable by a bracketed plus sign with a green font, along with a number that corresponds to the applicable bonus. For example a champion with 50 ability power who has an ability with an ability power ratio of 0.7, it will display "+35" (50 &times; 0.7) next to the corresponding value in the UI.

Items
NOTE: SOME OF THESE ITEMS' DESCRIPTIONS HAVE BEEN UPDATED FOR THE SEASON 3 PRESEASON PATCH.

Classic

 * : On use, grants +20-40 ability power (based on champion level) and +10% cooldown reduction for 4 minutes.
 * : On use, grants +20-40 ability power (based on champion level) and +10% cooldown reduction for 4 minutes.

Champion abilities
Note: Only the ability power buff effect of these abilities is shown here, to read more information on each of these abilities, follow the link on each of them.
 * adds 50% of his total magic resistance to his bonus ability power.
 * increases her ability power by corresponding to her percentage of missing health. The value increases depending on her level.
 * Increases the the ability power of the target by.
 * grants him ability power for 25 seconds.
 * aura grants herself and nearby allied champions bonus ability power while active.
 * grants himself ability power, and grants nearby allies half of that.
 * grants him ability power for 5 seconds upon activation.
 * permanently grants him 1 ability power when the ability kills a unit and passively grants him ability power when he kills a champion from any damage source.
 * grants him 3 ability power per level.
 * grants him 45 ability power.
 * grants him 1 ability power per 40 bonus health.

Masteries

 * increases your champion's ability power by per rank.
 * increases your champion's ability power by per champion level ( at level 18).
 * increases your champion's ability power by per rank.
 * grants +5 ability power while your spell is on cooldown.
 * upgrades your spell to increase ability power gained by 10%.

Runes
{|cellspacing="0" border="1" align="center" style="border-collapse:collapse; border:1px solid white; width:100%; text-align:center;" ! scope="col"|Name ! scope="col"|Type ! scope="col"|Tier 1 (Lesser) ! scope="col"|Tier 2 (Normal) ! scope="col"|Tier 3 (Greater) (Ability Power per level) 30 165 410 30 165 410 30  165  410  80 410 1025
 * and runes increase ability power.
 * rowspan="4" id="Force" |Force 
 * rowspan="4" id="Force" |Force 
 * bgcolor="#7E2217" |Mark
 * 0.06 per level (1.08)
 * 0.08 per level (1.44)
 * 0.10 per level (1.80)
 * bgcolor="#806517" |Seal
 * bgcolor="#806517" |Seal
 * 0.06 per level (1.08)
 * 0.08 per level (1.44)
 * 0.10 per level (1.80)
 * bgcolor="#2B547E" |Glyph
 * bgcolor="#2B547E" |Glyph
 * bgcolor="#2B547E"| 0.10 per level (1.80)
 * bgcolor="#2B547E"| 0.13 per level (2.34)
 * bgcolor="#2B547E"| 0.17 per level (3.06)
 * bgcolor="#4E387E" |Quintessence
 * bgcolor="#4E387E" |Quintessence
 * 0.24 per level (4.32)
 * 0.34 per level (6.12)
 * 0.43 per level (7.74)
 * rowspan="4" id="Potency" |Potency
 * rowspan="4" id="Potency" |Potency

(Ability Power) 30 165 410 30 165 410 Glyph
 * bgcolor="#7E2217" |Mark
 * 0.33
 * 0.46
 * 0.59
 * bgcolor="#806517" |Seal
 * bgcolor="#806517" |Seal
 * 0.33
 * 0.46
 * 0.59
 * bgcolor="#2B547E" |
 * bgcolor="#2B547E" |

30  165 
 * bgcolor="#2B547E"| 0.66
 * bgcolor="#2B547E"| 0.92
 * bgcolor="#2B547E"| 1.19

410
80 410 1025
 * bgcolor="#4E387E" |Quintessence
 * bgcolor="#4E387E" |Quintessence
 * 2.75
 * 3.85
 * 4.95
 * }

Neutral buffs

 * The buff grants +40 ability power (among other bonuses) for 4 minutes.

Trivia
Aside from, who may obtain any amount of ability power due to the passive effect of , and , who requires using a metagame mechanic not intended to be seen in gameplay (bonus magic resistance when AFK), the highest attainable ability power by a playable champion is 1874, on. To reach this amount, he must:
 * have a fully stacked and five.
 * have a full page of runes.
 * have the mastery and maximum ranks in the, , and  masteries.
 * possess the buff.
 * have consumed an.
 * have on cooldown.
 * be affected by a aura.
 * be affected by the auras of nearby and  abilities, and under the effects of.
 * have killed an enemy with the same setup with

This combination will result in having 1874 AP. The ghost spawned will have 3448 AP, though she is not a playable character.

Relevant mathematics:


 * AP(180120513083.166184040530203560)(10.250.05)1621.308
 * AP(180120583.166184040530203560(1621.3080.2))(10.250.05)1873.84808
 * ghost AP1621.3081873.848080.75(10.250.05)3448.309878