Experience/Core series/Relation to level

The amount of experience points a Pokémon has is tied directly to its level. Though the amount varies depending on species, always remaining consistent throughout an evolutionary family, a given amount of experience points will always set a Pokémon at the corresponding level. Wild Pokémon of any level will always have the base amount of experience required to reach that level when caught, as will Pokémon hatched from Eggs.

All Pokémon fall into one of six experience groups, four of which were introduced in Generation I, and two of which were introduced in Generation III. The main difference between these experience groups is the amount of experience points required to reach level 100, and thus, the amount required to reach each level. All those introduced in Generation I are only  of the level, while the two introduced in Generation III operate as  functions, changing the equation depending on the level range.

The original four functions, the ones for the Fast, Medium Fast, Medium Slow, and Slow groups, are. The two that were added in Generation III (Erratic and Fluctuating), however, are made by multiplying the cube of the level by a linear function of it (a negative slope one in the case of Erratic, going from 2 to 0.6; and a positive slope one in the case of Fluctuating, going from 0.48 to 1.64), making those functions effectively.

Though the various experience groups' level-up rates can be calculated using an equation, a is used in the games after Generation II to prevent game slowdown and a glitch associated with the Medium Slow formula.

In Generation V and Generation VII, the amount of experience gained is dependent on both Pokémon's levels: the lower the victor's level is compared to the defeated Pokémon, the more experience points the victor will gain. 