Calculating Odds Pre-Flop and Post-Flop

Knowing how to calculate odds will help you make many decisions in Texas Hold’Em: what cards to fold, what cards to play, what draws to play, and what bets to call.

Before the flop in Texas Hold’em, you’re going to have to rely on some basic memorization to calculate odds. For example, the chances of being dealt a pocket pair is 5.88%, Ace-King suited is less than 1%, Ace-King off-suit is a little over 1%, one Ace is 15%, suited cards is 24%, and connecting cards is 35%. If you have an Ace at a full table (with 8 players), there is a 35% chance that another player also has an Ace.

If you have two unpaired cards, there is a 32% chance you’ll make a pair on the flop. If you have two suited cards, there is less than a 1% chance of flopping a flush (but there’s a 10.9% chance you’ll flop a flush draw). If you have two connected cards, there is a little better than a 1% chance of flopping a straight (but there‘s a 10.5% chance you‘ll flop an open-ended straight draw). If you have a pocket pair, there is about a 12% chance of flopping three of a kind.

With this knowledge, you can make a more educated decision about which cards to play. One of the trickiest things you’ll need to manage is which draws to play. In order to calculate which draws are worth playing, you’ll need to master how to calculate pot odds. The easiest technique for doing this is by using the Rule of 2 and 4. First, understand that each card in the deck (52 cards in the deck, 13 of each suit) represents roughly 2%.

The first step is to know how to calculate outs. Let’s say you hold the 8 and 7 of hearts and the flop is 9 of hearts, 2 of hearts, and 6 of diamonds. This gives you a flush draw (8, 7, 9, and 2 of hearts) and a straight draw (6, 7, 8, and 9). “Outs” are the number of cards in the deck that can successfully complete your hand. In this case, any heart will make you a flush (13 hearts in the deck minus the 4 you already have equals 9 outs). Additionally, a 5 or 10 of any suit will make you a straight. With four 5s and four 10s in the deck, this gives you 6 more outs--be sure not to count the 5 and 10 of hearts twice. So, you have a total of 15 outs.

Before the turn card, you’ll multiply the number of outs you have by 4. In this case, 15 times 4 equals a 60% chance that you’ll make either the straight or the flush by the river. If another player makes a bet that is less than 60% of the total amount of chips you could win, you should call it. Don’t be blind to reading the other players at the table when making your decision however.

Now, let’s say the turn card is a 3 of diamonds, which doesn’t get you any closer to your straight or your flush. With only one more chance to make your hand, you’ll now multiply your number of outs by 2 (now a 30% chance of making either your straight or your flush). If there is $200 in the pot, and your opponent puts out a $100 bet (for a total now of $300 you could win), would the pot odds suggest a call or a fold?

As $100 represents 1/3 of the pot, you’d need to have a better than 33% of making your hand to justify a call. In this case, it just comes down to a few percentage points. If your gut feeling and your read of the opponent suggests you call the bet, do it. Otherwise, the math just doesn’t justify calling such a big bet on a draw…or even two draws.

Here is an article about when odds don't matter.