Experience (champion)

Champion experience is the way the champions level up periodically. This allows them access to new abilities or higher ranks of existing abilities. Also many base stats and runes scale as your champion levels up.

Gaining experience
There are various methods to get experience:
 * Champion kills: Killing an enemy champion rewards a player with an amount of experience determined by the level of the champion slain. The experience gained is equal to 75% of the total experience required for a champion to go from the slain champion's current level to the next level up. In other words, if a level 7 champion is slain, the total experience gained is 75% of the total experience required for a champion to go from level 7 to level 8, or 862.5 experience points. The experience reward will be increased if there is a positive level difference between champions (e.g. a level 5 champion killing a level 7 champion) and decreased if the level difference is negative.
 * Assists: A champion is given an assist after damaging an enemy champion that is then killed within 10 seconds. A champion granted an assist will evenly split the total experience reward for killing the enemy champion with all other players that received an assist or landed the killing blow or are within 1600 range of the killing blow.
 * Minions: Killing minions in League of Legends grants an amount of experience upon their death. The experienced gained by the champion is determined by the type of minion as well as the current length of the game. Experience from minion deaths is split between all champions within 1200 range.
 * Turrets: Whenever an enemy turret is destroyed, all champions of the team are granted 30 experience.
 * Neutral monsters: Each type of neutral monster in League of Legends gives a different amount of experience upon death. Experience points from neutral monsters are split between every allied champion within an 400-unit range.
 * Epic monsters: Epic monsters grant experience rewards for an entire team of champions regardless of the location or status of those champions.

Increasing experience gain
Note that experience gained stacks additively.

Champion abilities

 * hidden passive allows her to passively give 5 experience points every 5 seconds to nearby allied champions that have a lower level than her.
 * passively and globally increases his and his allies' experience gain by 8%. This bonus is lost while he is dead.

Masteries

 * in the fourth tier of Utility tree increases experience gain by 1.25 / 2.5 / 3.75 / 5 %.

Runes

 * runes increases experience gain by 2% each.

Neutral buffs

 * Crystal Scar's Aura grants every champion passive experience gain while playing on the Dominion game mode. (7.2 exp points per second.)

Other
V1.0.0.138 changes:
 * Experience split when two or more champions are present increased; situations with two or more champions splitting experience now earn 30.4% more total experience than solo, up from 26.1%.

Experience needed to level up
The following describes the amount of experience required to go from one level to the next on Summoner's Rift:

Only 80% of this experience is required to level up on the Twisted Treeline, and the Crystal Scar has its own experience requirements, which are not exactly but are close to 75% of the values in the above chart.