Two Plus Two Older Archives Calculating drawing odds on the flop
 FAQ Members List Calendar Search Today's Posts Mark Forums Read

#1
11-01-2002, 03:28 AM
 Eric P Senior Member Join Date: Oct 2002 Location: chicago Posts: 334
Calculating drawing odds on the flop

Can someone tell me the formula to doing odds combining the turn in the river. I know most the important ones but i'm not 100% how to do the calculations

For example. what are the odds to improve if you flop trips (banning straights and flushes)
I see it as:
you've seen 5 cards so 47 left in the deck, 7 ways to improve (board pairs or you quad) so 7/45 or 15%, then on the turn you have 10 outs so 10/45 or 22%. Do i simply add these percentages? If some one could explain this to me i would apprciate it. I had just been adding them but i want to make sure i'm right.
#2
11-01-2002, 11:42 AM
 marbles Senior Member Join Date: Oct 2002 Location: Wauwatosa, WI Posts: 568
Re: Calculating drawing odds on the flop

When calculating probabilities on the flop, particularly "what's my probability of improving at all," it's often easier to calculate the probability of the opposite, then taking 1 minus the result.
Example:
You have 99. Flop is 49A. At this point, let's take A9 and AA out of the equation, and assume that any A, 9, or 4 will be a good thing. Since there are 7 such cards (3 A's, 3 4's, and one 9), the probability of success (call it 'p') is 7/47 (.149). Equally important, the probability of failure is 1-p, or .851.
Now, let's say the turn doesn't help you, and the board now reads 49A[X], [X] being any non-A, 9, or 4. Now your probability of success on the river (call it 'q') is 10/46 (can you see where the 10 and 46 come from?), or .217. This time, the probability of failure, 1-q, is .783.

Now, if you're on the flop, and you want to calculate the probability of improving at all, you could calculate:
The probability of improving on the turn and not the river, the probability of improving on the river and not the turn, and the probability of improving on both (adjusting the numbers for the different-looking river scenario).

Simpler, though, you can calculate the probability of improving on NEITHER:
(1-p)*(1-q)=.851*.783=.666. Subract this number from 1, and you find that, as of the flop, you have a 33.3% chance of improvement.

Clear as mud?
#3
11-01-2002, 02:44 PM
 Jim Brier Senior Member Join Date: Sep 2002 Location: Las Vegas, NV Posts: 189

(n/t)
#4
11-03-2002, 02:50 AM
 Fitz Senior Member Join Date: Sep 2002 Location: Kansas City Posts: 303
Re: Calculating drawing odds on the flop

So, if I flop 4 to a flush, the way I would calculate my percentage of making it by the river would be:

1-9/47= .8085 * 1- 9/46= .8043 = 65% of not making it by the river, or ~ 1 in 3 times I should make my flush by the river.

Let me know if I am calculating this properly.

Thanks,

#5
11-04-2002, 12:13 AM
 Eric P Senior Member Join Date: Oct 2002 Location: chicago Posts: 334
Re: Calculating drawing odds on the flop

Ok that's what i thought. Thanks.

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is Off Forum Rules
 Forum Jump User Control Panel Private Messages Subscriptions Who's Online Search Forums Forums Home Two Plus Two     Two Plus Two Internet Magazine     About the Forums     MOD DISCUSSION     ISOP General Poker Discussion     Texas Hold'em     Beginners Questions     Books and Publications     Televised Poker     News, Views, and Gossip     Brick and Mortar     Home Poker     Poker Beats, Brags, and Variance     Poker Theory Limit Texas Hold'em     Mid- and High-Stakes Hold'em     Medium Stakes Hold'em     Small Stakes Hold'em     Micro-Limits     Mid-High Stakes Shorthanded     Small Stakes Shorthanded PL/NL Texas Hold'em     Mid-, High-Stakes Pot- and No-Limit Hold'em     Medium-Stakes Pot-, No-Limit Hold'em     Small Stakes Pot-, No-Limit Hold'em Tournament Poker     Multi-table Tournaments     One-table Tournaments Other Poker     Omaha/8     Omaha High     Stud     Other Poker Games General Gambling     Probability     Psychology     Sports Betting     Other Gambling Games     Rake Back     Computer Technical Help Internet Gambling     Internet Gambling     Internet Bonuses     Software 2+2 Communities     Other Other Topics Other Topics     Sporting Events     Politics     Science, Math, and Philosophy     The Stock Market

All times are GMT -4. The time now is 09:57 PM.