Around 5,000 steps but each individual Pokemon has different hatching rates
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you can't hatch a pikachu egg on diamond, it hatches in to a pichu.
It depends on the Pokemon you are hatching.
It takes between 9,180 and 9,434 steps to hatch an Eevee egg. You can halve this time if you have a Pokemon with the Flame Body or Magma Armor ability in your party.
5355 steps.
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about 7,000 steps
you can't hatch a pikachu egg on diamond, it hatches in to a pichu.
It depends on the Pokemon you are hatching.
It takes between 9,180 and 9,434 steps to hatch an Eevee egg. You can halve this time if you have a Pokemon with the Flame Body or Magma Armor ability in your party.
5355 steps.
it counts what kind of Pokemon it is
It takes a maximum of 5,120 steps for a Nidoran Egg to hatch however it could be less than that due to the fact that eggs are randomly generated.
it will take 999999999999 steps to hatch a egg
It takes 9,180 steps or 36 Egg Cycles to hatch an Eevee.
I tested it on my platinum game and it took me 11,475 steps to hatch my gible egg i don't know if its the same for dimond or pearl.
It takes a Riolu Egg a maximum of 6,400 steps to hatch however each Riolu Egg is different so it could hatch earlier depending on the Egg and other factors involved.