Howdy

This might not be easily explained here, but i wondered if anyone knew nonetheless.

Sometimes watching tourny's on the TV, when 2 players go All-In, and turn over their cards, they will say what the odds of them beating their opponent are and are normally within a couple of % of what the TV show is saying, and i just wondered how on earth they do it so quickly?

I can do Turn / River odds without any problems, but can't quite get my head around working out pre-flop odds

Anyone?