straight odds

[Jeremy J]

I know this is a rookie question, but can someone give me the math on how to figure out your odds of hitting your straight by the river when you've flopped an open ender.

[TomCollins]

Percentage of missing:

(45-8)/45*(44-8)/44 = .6727.

So percentage of making is:

1-.6727 = .327.

So roughly 2-1.

[Lost Wages]

/images/graemlins/blush.gif Must be sloppy math day.

It's (47-8)/47*(46-8)/46 = .685
1-.685 = .315
.685:.385 = ~2.2:1

Lost Wages

[TomCollins]

Bah, you suck.

[Vulpine]

There’s a quicker way to approximate this using the “rule of four.” You have 8 cards that can complete your two way straight draw by the river. Multiply these outs by 4 to get a 32% probability of completing your straight by the river. Convert this probability to the odds against making the draw by the taking (100 -32)/32 = 2.125. Most books will recommend that you not use these odds to make your decision because a turn card can dramatically change your situation. Of course the odds of making a two way straight draw on the turn are (47 unseen cards – 8 outs)/(8 outs) = 4.875 and the odds of making a two way straight draw on the river are (46 unseen cards – 8 outs)/(8 outs) = 4.75.

[TomCollins]

Just remember this rule is an approximation and not exactly right. But your decisions are rarely going to be affected if you are off by a percent or two.

[thomas_sfbay]

Multiply your outs (8) by 4 for a 32% chance of hitting the open ender. Granted this is a rough estimate but its within a couple of percentage points of being exact.

On the turn the same 8 outer would be a 16% chance... 8 outs times 2 = 16%.

Thomas

[Huhmare]

Who wants to know the odds of getting the straight by the river? The odds from flop to turn and from turn to flop are more of a use. You can't know how many bets there is going to be on the turn

[Jeremy J]

If your only in the hand with a couple players you can have a pretty good idea how many bets, and if you're short stacked that info helps to know if you should call in a big pot. But thanks for the constructive criticism. /images/graemlins/wink.gif