To really master texas hold’em the next step after calculating the pot odds, is to calculate your equity (in other words, the probability for you to win the pot). In order to calculate your equity, multiply the number of your outs by 4 on the flop (or by 2 on the turn). This way you are going to get the percentage of probability for you to win the pot. For example, if you have a flush draw you have 9 outs on the flop (9 . 4 = 36 % probability to get a better hand).
Since the pot odds are expressed as proportion, you should express these percentages as a ratio in order to be able to make a comparison. Since the maximum percentage is 100, your equity, expressed as a proportion, is equal to 64 – 36 (i. e. 64 times you are not going to get a better hand, and 36 times you are going yo get it).
If you make the right part of the proportion to be equal to 1, your equity will be 1,7 – 1. In other words, for each case you manage to complete your flush draw, there are 1,7 cases when you won’t complete them. In case you don’t want to be so precise when you calculate the pot odds (the maths at the table should not necessarily be very precise), you can just notice that 64 is greater than 36 a little less that twice. As a matter of fact, it does not much difference whether the proportion is 1,6; 1,7; 1,9 to 1 – you can even say it 2 to 1 and that will be enough to decide to call or not to call.