Originally Posted by disco5tu
ye it gives a good approximation, but is inaccurate sometimes. for example, if you have a flush draw + 2 overs otf (9 outs to flush + 6 outs to pair = 15 outs).
15*4= 60. although your equity will be good, it will not be this good.
i think the 'rule of 4 and 2' can sometimes overestimate big draws.
Right. A useful adjustment for the rule of 4: apply the rule, then if outs greater than 8, subtract (outs - 8) from the percentage. E.g., for 15 outs with two cards to come: apply the rule of 4 to get 60%; then subtract (15 - 8) or 7 from 60 to yield 53%. The actual probability is 54%.
For 12 outs, such as flush draw plus gut shot: rule of 4 gives 48%; adjustment gives 44%; actual is 45%.