[Guernica4000]

Here's another way to get closer percentages than using the 4% method.

For example:
With a flush draw on the flop you have nine outs so 4x9= 36% but for every number of outs over 8 take that number and subtract it from the number of total outs (9-8=1) (36%-1=35%) and you get the exact number.

Say you have 15 outs: 15x4=60% then (15-8=7) (60%-7=53%)

Your 15 outs are 53% favorite.

For 21 outs. 21 x 4= 84% then (21-8=13) (84%-13=71%)

This is off by 2% from Card Player but it gets you closer to the real % than just multiplying the outs by 4 and it is easy to do in your head.