Pokémon breeding/Games/How to breed/Breeding rate

The chance of any two Pokémon producing an Egg is determined by their species (two are the same species, while Bulbasaur and  are not) and their Original Trainers. In Generation III or later, the Day-Care Man will describe the two Pokémon's compatibility when the player speaks to him. In these games, an Egg may be generated after every 256 steps the player takes. The chances of finding an Egg are different in Generation II, and the compatibility can be checked by interacting with the Pokémon themselves instead of with the Day-Care Man. In these games, there is a chance to generate an Egg after every step.