*Originally posted by Aimboy*

Fastest way is 2-4 rule, if you have 7 outs you multiply it by 2, when you need percentage of hitting your draw from flop to turn or you multiply it by 4 when you need % from flop to river. So you have smth like 28% chance and then you use this equation: odds = (1/percentage) - 1, which gives you 2,57:1 odds.

You can also use this formula:

flop to river: 1-[((47-outs)/47)*((46-outs)/46)]

The 2-4 formula is very effective when you play and don't have time to make accurate calculations, but if you would like to know the exact formula it's pure probability equation...

First you have to calculate the chances for you hitting one of the outs:

"you hit turn" + "you hit river after you hit turn" + "you hit river after you missed turn" = chances to hit

"you hit turn" = outs/47

"you hit river after you hit turn" = [(outs - 1)/46]*[outs/47]

"you hit river after you missed turn" = [outs/46]*[(47 - outs)/47]

So, for your case that's:

7/47 + (6/46)*(7/47) + (7/46)*(40/47) = 0.298

From this on you transform "chances to hit" into odds:

1/"chances to hit" - 1 = odds

For your case:

1/0.298 - 1 = 2.36

It's a bit long, but I hope it's clear.

Regards,

burek2000