I know of the EV measurer psypoke has, but I was wondering if anyone knows a site I can go to that all you have to do is input all of a Pokemon stats and its nature.

Since there's only one possible EV-DV-Nature-HiddenPower combination for every different stats arrangement I think this should be possible.

Don't know of a site, but I think there are lots of different combos for each stat value. However, if you know one (DVs, for instance), then yes, there should be a way to figure out the other.

Edit: Hmm... I don't know if that statement is precisely true... but if it is, then it should be possible, yes... But I haven't heard of a calculator that does it.

I made a mistake in my original statement, it's fixed now.

I don't think there'd be a way even if you knew what HP was.

You see, You could have a 31 DV for a Pokemon with 0 EPs for that stat, and another with 29 or lower DVs with 252 EPs, it will have higher stats than the other one.

If you want to figure out what eps your pokes has though, you can trade your pokes to Emerald and use the Pomeg, Hondew, etc. Berries to lower EPs.
Each one lowers by 10 EPs, so you won't get exact amount of eps (Like 97 EPs would be 10 Berries), but you'll get the idea of how many it has. (I'm guessing that it does it like that, but I haven't done it myself, so it could be different)

EDIT: Forgot [ / color]

Well so much for my theory.

Thanks anyway.