In a nut shell if you have 8 outs on the flop:

You have 4 x 8 = 32% to hit one of your outs.

On the turn:

You have 2 x 8 = 16% to hit one of your outs.

These are rough approximations. Been a long time but I think the exact math is like (>2.1x) per street.


As far as odds, these are usually represented in ratios. (e.g. 3to1 and 8to1)

So if you have 8 outs on the flop you need to be getting better than 2to1 to call.

NOTE: This straightforward math is for limit hold-em. In no-limit hold-em you would want to consider the amount of money your opponent has left behind in his/her stack. This concept is called "implied odds" and it revolves around the idea that you may be more willing to take slightly worse odds on a draw considering if you hit it against that particular opponent he/she may pay you off an amount sufficient to hedge taking a SLIGHT disadvantage. This concept applies more to cash games than tournaments, but some late stages of very large tourneys also provide stacks that allow for such consideration.