How long does it take to sober up?
It really depends on what you were doing that you need to "sober up" from. If it's alcohol, then it also depends on how much you drank, etc...the body processes about a can of beer, a glass of wine or a shot of hard liquor in one hour.
So if you had say, six beers, it'd take you about six hours to go completely sober, assuming that you're of average size and if you drank them all at once.
a long long time