How to calculate poker odds: outs, the 4/2 rule and pot odds
Four steps, all of them arithmetic you can do in the three seconds you actually get at the table.
The short version. Count your outs — the cards that make your hand the winner. Multiply by 4 if the turn and river are both to come, by 2 if only the river is left. That is your equity as a percentage. Then work out your pot odds: the amount you must call divided by the pot after your call. Call when the first number is bigger than the second.
Step 1: count your outs
An out is an unseen card that turns your hand into the best hand. Counting them is the only part of this that takes practice, because it depends on reading the board rather than doing sums.
Start from what is missing. You hold Jh Th, the board is 9c 8d 2s. You have nothing yet. What makes you the winner? Any queen and any seven complete a straight: four queens plus four sevens is eight outs. That is an open-ended straight draw, and eight outs is the number to remember for it.
Now hold Ah 4h on Kh 9h 2s. Nine hearts remain in the deck, so the flush draw is nine outs. The three remaining aces probably win too, but not always — so count the nine, note the aces, and do not pretend they are worth a full out each.
| Draw | Outs | Why |
|---|---|---|
| Gutshot straight draw | 4 | You hold J9, the board is 8-7-2: only a ten finishes it. |
| One pair, hoping to improve | 5 | Two cards pair your kicker, three make trips. |
| Two overcards, no draw | 6 | AK on a 9-8-3 board: three aces and three kings. |
| Open-ended straight draw | 8 | You hold JT, the board is 9-8-2: a queen or a seven. |
| Flush draw | 9 | Two hearts in your hand, two on the board, nine hearts left. |
| Flush draw + gutshot | 12 | Nine flush cards plus three more straight cards that are not hearts. |
| Flush draw + a pair | 14 | Nine flush cards, two to trips, three more to two pair. |
| Open-ender + flush draw | 15 | The monster draw: more equity than one pair has. |
Two rules keep your count honest. Only count cards that win — if the ten that makes your straight also makes an obvious flush for the player betting into you, that out is a fraction of an out. And do not count the same card twice: a queen of hearts that completes both your flush and your straight is one card, not two.
Step 2: the rule of 4 and 2
Outs become a percentage with one multiplication. Two cards to come, multiply by four. One card to come, multiply by two. Nine outs on the flop is about 36% to get there by the river; on the turn, about 18%.
The shortcut is good up to about nine outs, then it starts to flatter you. The reason is simple: four times your outs is really your turn chance plus your river chance, and those two overlap on the boards where you hit twice. The table below shows the true figures next to the shortcut, and the gap opening up as the draws get bigger.
| Outs | True, flop to river | True, turn to river | Rule of 4 | Rule of 2 |
|---|---|---|---|---|
| 1 | 4.3% | 2.2% | 4% | 2% |
| 2 | 8.4% | 4.3% | 8% | 4% |
| 3 | 12.5% | 6.5% | 12% | 6% |
| 4 | 16.5% | 8.7% | 16% | 8% |
| 5 | 20.4% | 10.9% | 20% | 10% |
| 6 | 24.1% | 13.0% | 24% | 12% |
| 7 | 27.8% | 15.2% | 28% | 14% |
| 8 | 31.5% | 17.4% | 32% | 16% |
| 9 | 35.0% | 19.6% | 36% | 18% |
| 10 | 38.4% | 21.7% | 40% | 20% |
| 11 | 41.7% | 23.9% | 44% | 22% |
| 12 | 45.0% | 26.1% | 48% | 24% |
| 13 | 48.1% | 28.3% | 52% | 26% |
| 14 | 51.2% | 30.4% | 56% | 28% |
| 15 | 54.1% | 32.6% | 60% | 30% |
True figures from the deck arithmetic: 47 unseen cards on the flop, 46 on the turn. The full 1–20 version is on our poker odds chart.
Step 3: turn the price into a percentage
Pot odds are the other half of the decision, and the easiest version to use is a percentage so it can be compared with your equity directly.
Break-even equity = the amount you call ÷ (the pot before your call + the amount you call)
Facing a $50 bet into a $100 pot, you are calling $50 into a pot that will be $200 once your chips go in. That is 25%: you need to win one time in four to break even. The same maths for every common bet size:
| Bet size | Example | You call | Final pot | Equity you need |
|---|---|---|---|---|
| Quarter pot | $25 into $100 | $25 | $175 | 14.3% |
| Third pot | $33 into $100 | $33 | $166 | 19.9% |
| Half pot | $50 into $100 | $50 | $200 | 25.0% |
| Two-thirds pot | $67 into $100 | $67 | $234 | 28.6% |
| Full pot | $100 into $100 | $100 | $300 | 33.3% |
| One and a half pot | $150 into $100 | $150 | $400 | 37.5% |
| Two times pot | $200 into $100 | $200 | $500 | 40.0% |
Four numbers cover almost every hand you will play: a third of the pot needs 20%, a half needs 25%, a full pot needs 33%, twice pot needs 40%. Learn those and you never have to do the division again. The mechanics in more depth are in pot odds.
Step 4: compare, then adjust
Equity bigger than the price means calling makes money. Equity smaller means folding does. Then two adjustments, because the hand does not stop on this street.
- Subtract for the bets still to come. The rule of 4 prices both the turn and the river, but you are only buying one card when a second bet is coming that you will have to pay. Facing a flop bet with a plan to fold the turn, use the rule of 2, not the rule of 4.
- Add for implied odds. When you hit a draw nobody can see, you often win more than the pot that is out there now. That extra money is a real part of the price, and it is why a flush draw can call a bet that the raw percentage says is too expensive.
Three worked hands
Hand 1: the easy call
$1/$2 cash, you are on the button with Ah 4h. The flop is Kh 9h 2s and the pot is $50. Your opponent bets $25.
- Outs: nine hearts. Three aces are probably good too, so call it nine and a bit.
- Shortcut: 9 × 4 = 36%.
- Price: $25 into a final pot of $100 — you need 25%.
- The real number: face up against top pair (say Kd Qc), the exact count over all 990 turn and river combinations is 45.9% — the ace and the backdoor outs are worth more than the shortcut credited.
36% beats 25%, so this is a call before you even consider that you are actually ahead. With this much equity, raising is usually better than calling: you have a hand that wants the pot to grow.
Hand 2: the fold the rule already told you about
You hold Jc 9d. The flop is 8h 7d 2c, giving you a gutshot: only a ten completes the straight. The pot is $40 and your opponent bets $40.
- Outs: four tens.
- Shortcut: 4 × 4 = 16%.
- Price: $40 into a final pot of $120 — you need 33.3%.
- The real number: against an overpair such as As Ad, exactly 20.3% of the 990 runouts.
Even the true figure, which is better than the shortcut because your jack can sometimes pair and win, is nowhere near 33%. Fold. This is the most common leak in small-stakes poker: paying a full-pot price for a four-out draw because the straight would be so pretty.
Hand 3: the turn decision the 4 rule gets wrong
You hold Jc Td on a board of 9h 8d 2c, and the turn is the 3s. Still an open-ender, still eight outs, but only one card left. The pot is $90 and your opponent bets $60.
- Shortcut: one card to come, so 8 × 2 = 16%.
- Price: $60 into a final pot of $210 — you need 28.6%.
- The real number: against As Ad, exactly 18.2% — eight of the 44 remaining cards win.
Fold, unless you are confident of winning a lot more on the river when you hit. Had you used the rule of 4 here you would have talked yourself into 32% and made a call that loses roughly a fifth of a pot-sized bet every time. The single most expensive mistake in this whole topic is using the flop multiplier on the turn.
Exact figures computed by the engine behind our poker equity calculator: 990 runouts for the flop hands, 44 for the turn hand. Type any of them in to check.
Five mistakes that cost real money
- Using the rule of 4 on the turn. It doubles your equity and turns folds into calls. One card left means multiply by two, always.
- Counting outs that lose. The card that makes your straight can make their flush. Count those at half value or not at all, especially against a player who keeps betting.
- Forgetting the bets still to come. Calling $25 on the flop is rarely a $25 decision. If you will face a $70 turn bet and fold it, you paid $25 for one card, so price it with the rule of 2.
- Ignoring who is left to act. Pot odds in a three-handed pot change the moment someone behind you raises. Position is part of the price.
- Treating a percentage as the whole decision. Odds tell you whether a call breaks even. They say nothing about whether raising would have been better. Very often, with a big draw, it is.
Where to take this next
- What is equity in poker — the definition, and why realised equity is lower than raw equity.
- Pot odds and expected value — the price side, and the money side.
- Poker odds chart — outs, odds and equity on one printable page.
- Equity calculator — check any hand exactly, including against a whole range.
- Preflop charts — which hands to be in these spots with in the first place.
- Variance calculator — how long it takes for correct odds decisions to show up in your results.
Frequently asked questions
How do you calculate poker odds quickly in your head?
Count your outs — the cards that turn your hand into a winner — then multiply by four if two cards are still to come, or by two if only the river is left. Nine outs with two cards to come is about 36%, and the true figure is 35.0%. Compare that percentage with the share of the final pot your call represents and you have your answer.
What is the rule of 4 and 2 in poker?
It is a shortcut for turning outs into a percentage. On the flop, with the turn and river both still to come, multiply your outs by four. On the turn, with only the river left, multiply by two. It is accurate to within a point or two up to about nine outs, then starts to overstate the big draws — fourteen outs reads as 56% but is really 51.2%.
Why does the rule of 4 overstate big draws?
Because it double-counts the boards where you hit twice. Multiplying by four is really adding your turn chance and your river chance together, and those overlap. With one or two outs the overlap is tiny; with fifteen outs it is significant. Above about nine outs, multiply by four and then subtract the amount by which your outs exceed eight.
How do I calculate equity in poker rather than odds?
Odds from outs only count the times you improve. Equity is your full share of the pot, including the times you win without improving and the times you make a hand that still loses. For an exact figure you have to count every possible board, which is what our equity calculator does — 990 boards from the flop, 1,712,304 preflop.
What are pot odds and how do they relate to outs?
Pot odds are the price of the call expressed as a share of the final pot: your call divided by the pot after your call goes in. Facing a pot-sized bet you are paying 33% of the final pot, so you need 33% equity to break even. Outs give you the equity side; pot odds give you the price side. Call when the first is bigger than the second.
Should I count all my outs?
No. Discount any out that completes a better hand for your opponent. If you hold a gutshot on a two-tone board and the card that makes your straight also makes their flush, that out is worth less than a full one. Players who count every out generously talk themselves into calls that lose money.
Do pot odds still apply when there is more betting to come?
Only partly. Pot odds assume the hand stops here, which on the flop it rarely does. If you call a flop bet with a draw, budget for the turn bet too — or plan to fold to it and accept that you paid for one card, not two. The counterweight is implied odds: the extra money you expect to win on later streets when you do hit.