Calculation for Percentage of Hitting Hand Via Outs

Can anyone remind me of the simple calculation used to work out the percentage chance of you hitting a hand via the number of outs you have on the flop and turn???

Cheers people, FTR is the shizzle, whateva that means...

Basic rule of thumb
4%*number of outs to hit by the river after the flop
2%*number of outs to hit by the river after the turn

A bix more complex but a little more accurate
After the flop to hit the river
4% for the first 10 outs
3% for any out after 10
So if you have 13 outs its 49%

After the turn to hit the river
2.2% per out

o - outs

o/47 + (47-o / 47) * (o/46)

13 outs is:

13/47 + (34 / 47) * (13/46) =48.1%

that's on the flop
simply 13/46 on the turn


the formula can also be written as

o/47 * (1 + [{47-o}/46])

or

o/47 * (93-o) / 46

so if you know what the chance of making it by the turn is, subtract outs from 93 and divide by 46 and multiply by that chance

do not attempt this during the game unless you're sklansky though

the shorter way:

the amount you multiply the outs by is 4.3
BUT take away from that amount outs times 0.046
so for 13 outs the multiplier is 4.3 - (13 * 46) / 1000 - around 3.7
3.7 * 13 = 48.1

It's correct to 3 decimal places and doable in your head