how many outs is a backdoor flush?

[godofPOPOV]

if you have a backdoor flush draw, or a backdoor straight draw, or a backdoor straight-flush draw how many outs should you add to your calculation?

[jay_shark]

a)10c2/47c2 =0.0416 or 4.16% . Now we divide by 4 using the 4X rule . This means that if you have x outs , then the approximate probability that you'll hit on the turn or river in percentage form is 4x .

b)If you hold something like A-9 suited and the flop is 10-j-2 . You may hit a queen and a king in no specific order with probability 1.48% of occurring or you may hit q-8 or 8-7 which all have the same probability of occurring .

1.48%*3 = 4.44% . Again we divide by 4 to give us the number of outs which is about 1.11 and you might as well just round it down to 1 .

c)Using the same example as above , there are three ways you can hit your straight flush . (2*1/47*1/46)*3 or 2/(47c2)*3 = 0.00555 =0.555% which when we divide by 4 is inconsequential to even consider .

[KipBond]

I think a good estimation would be to calculate % as if you are on the river, and square it. 20% (9 outs) = 20%*20% = 4%. OESFD = 15 outs = 33% * 33% = 11%.

[TrainHardDieHard]

According to sklansky, a backdoor flush draw is one out - need runner - runner flush cards - which equates to something around 4%

[Doug Funnie II]

I think in small stakes holdem they count backdoor flush draws as 1.5 outs. I assume this is because if you don't hit on the turn then your draw is completely worthless, but if you do hit then your draw becomes pretty strong when the bets are doubled. That was a limit book though, so if its no-limit facing a flop allin and for some reason you think the backdoor flush draw might add enough equity to call then its worth only 1 out.

[Siegmund]

The way I look at a backdoor flush draw on the flop is to say "I have a 10/47 chance of buying 9 extra outs on the turn," which is the equivalent of 1.91 outs. The people who call it one out mean that your chance of eventually making your hand is about the same as if you had one extra out twice -- but, in the real world, we choose whether to call a flop bet, and then choose again whether to call a turn bet, so I count it as ~2 on the flop and then 0 or 9 on the turn as appropriate.

Three to a straight is more complicated. You are 8/47 to buy 8 extra outs (you turn OESD), AND 8/47 to buy 4 extra outs (you turn a gutshot). If you have enough value that you're sure you expect to see the river if the gutshot comes -- say TPTK and the gutshot will move you up from 5 to 9 outs -- then the 3-straight is adding the full 8/47*8+8/47*4~2.04 outs on the flop. If you plan to fold a gutshot to a turn bet, it's only 8/47*8~1.36 now.

Each of these suffers a small downward adjustment if one of your backdoor cards is already one of your other outs, of course.