Originally Posted by dj11
Caveat; there is the weird situation where each of the other players fold before showdown. Only a fool would fold here, or some one colluding or chip dumping.
If someone has gone all in for less than one big blind, and everyone else folds to the player in the big blind, then those two players contest the pot.
In this case, a player has gone all in for 10. If everyone folds to the big blind, who's already in for 20, then he gets 10 back, there's 30 in the pot (including the folded small blind) and both the all-in player and the big blind roll over their hands.
The all-in player cannot
win the pot without a showdown.
Aside from this, everyone's got it right: there's 30 in the main pot in this instance, as the all-in player can't win any more than 10 from any other player in the hand.