There are only five ways to gain experience. Experience isn't gained over time.
- Killing a champion: Gives 50% of the experience required to reach the slain champion's next level (not current level). This is increased/lowered by 7% per level difference if the target is higher/lower level and can't be lower than 20%.
- Assisting: The experience granted for killing, including this increase (see above), is divided equally if there were assistants.
- Proximity to a minion death: Regardless of whether it was last hit or killed by another source.
- Structures (except outer turret and nexus): Inhibitors and turrets grant XP, except outer, different ones grant different amounts.
- Monsters: Different monsters give different amounts. If the killer is of a low level (not compared to the monster) it's upped by 50%. All XP goes to the killer.
- See Jungling.
Increasing experience gain
Note that experience gain modifiers stack additively.
- A non-displayed passive that used to possess prior to her rework granted 5 experience points every 5 seconds to nearby allied champions that had a lower level than her.
- Murder Bridge's Aura grants every champion passive experience gain.
- Crystal Scar's Aura grants every champion passive experience gain while playing on the Dominion game mode (7.2 exp points per second).
In addition, when more than 1 champion is sharing experience, 30.4% extra experience is split among all champions.
- Two champions each gain 65.2%
- Three champions each gain 43.46%
- Four champions each gain 32.6%
- Five champions each gain 26.08%
Experience needed to level up
The Crystal Scar has its own experience requirements, which are not exactly but are close to 75% of the values on Summoner's Rift.