Three Outs Example
Pocket Cards Community Cards
A pretty dangerous looking flop for you. You figure you need to hit that Ace to have a chance at winning. What are the chances of hitting that one specific overcard? Well you have three outs. The remaining three Aces in the deck. On the turn it's 6.383%. Chance of getting it on the turn or river is 12.488%. If you miss on the turn and have to hit it on the river, the chance is 6.522%.
Note: In this example, we're ignoring the chance of hitting two running cards to make a straight.