Originally Posted by edc1
i wasnt aware it was flawed i use the 4-2 rule its fast and easy it doesnt have to be perfect to be effective-i do like four dogs expelenation of it seems like its spot on
its only slightly flawed, unlike OP who said seriously flawed.
When you have more than 8 outs it isn't as accurate, i.e. if you have 15 outs on the flop with an OESD and Flush Draw you have 15 outs but that isn't 60% (15 * 4)
There is a modified version whereby every number over 8 you subtract that from the final total, so in example above
15 outs x 4 = 60 - 15 is 7 above 8 so take off 7 and the answer is 53%
See pic below and compare the actual odds (Turn or River) to the 4 2 Rule column and Modified column. As you can see the difference gets bigger in the normal 4 2 Rule, whereas in the modified it stays pretty close.
At 20 Outs Actual is 67.53, 4 2 Rule is 80 and Modified 4 2 is 68