If you’re sitting in a cardroom and don’t have the benefit of a laptop at your fingertips or a mag in your hands, a quick way of figuring your chances is to use the four/two rule. On the flop with two cards to come each ‘out’ adds roughly a 4% chance of making your hand. On the turn with one card left each ‘out’ adds roughly a 2% chance of making your hand.

For example, if you have a four-card flush after the flop you have nine outs. With two cards to come, you multiply the nine by four, which gives you a 36% chance of making the flush. The chart shows the true odds at 35%. With one card to come you multiply nine by two and get 18%. The chart shows that the true figure is 19.6%. So, it’s not completely accurate but it’s pretty close, and an easy calculation to do in your head when you need to make the right decision.