Poker outs and the rule of 2 and 4
Outs are the cards that win you the hand. The rule of 2 and 4 turns them into odds: multiply your outs by 4 on the flop (both cards to come) or by 2 with one card to come. It’s close for small draws and overestimates big ones — the finder below counts your real outs and shows the exact odds side by side.
Outs finder
▼ You’re behind You: High Card, King. Them: Pair of Kings.
9 outs
| Chance to hit | Rule | Exact | Equity |
|---|---|---|---|
| Next card, ×2 | 18% | 20.0% | — |
| By the river, ×4 | 36% | 36.4% | 38.0% |
Rule: 9 outs × 2 or × 4. Exact: 9 outs among the 45 unseen cards (both hands are known, so not the usual 47). Equity: your share of the pot over all 990 possible turn-and-river run-outs — 1.6 points higher than the outs math, because two running cards (runner-runner) add equity the outs count misses.
What are outs in poker?
An out is an unseen card that improves your hand to the likely winner. You count them when you’re behind with a draw: a flush draw needs one more card of its suit, an open-ended straight draw needs one of two ranks. On the flop you haven’t seen 47 cards — 52 minus your two and the three on the board — and on the turn, 46.
| Draw | Example | Outs | Turn + river | One card |
|---|---|---|---|---|
| Pocket pair to a setthe two remaining fiveson | on | 2 | 8.4% | 4.3% |
| Gutshot straight drawthe four tenson | on | 4 | 16.5% | 8.7% |
| Two pair to a full housetwo kings, two nineson | on | 4 | 16.5% | 8.7% |
| Two overcardsthree aces, three kingson | on | 6 | 24.1% | 13.0% |
| Set to a full house or quadsthree kings, three fours, the last eighton | on | 7 | 27.8% | 15.2% |
| Open-ended straight drawfour tens, four fiveson | on | 8 | 31.5% | 17.4% |
| Flush drawthe nine hearts lefton | on | 9 | 35.0% | 19.6% |
| Flush draw + gutshot9 hearts + 3 non-heart eightson | on | 12 | 45.0% | 26.1% |
| Flush draw + open-ender9 hearts + 3 tens + 3 fiveson | on | 15 | 54.1% | 32.6% |
“Turn + river” is the chance of hitting at least once from the flop when you see both cards (47 unseen); “One card” is the chance on the river from the turn (46 unseen). When a card helps two draws at once — the 10♥ above completes both the flush and the straight — count it once: that’s why a flush draw plus an open-ender is 15 outs, not 17.
The rule of 2 and 4
Doing 1 − (38/47 × 37/46) in your head mid-hand isn’t practical, so players use a shortcut. Each out is worth about 2% per card to come:
- Count your outsCount the unseen cards that would give you the best hand. Count each card once, and leave out cards that also give your opponent a better hand.
- Multiply by 2 or 4On the flop, if you will see both the turn and the river (for example, you are all-in), multiply your outs by 4. With one card to come, multiply by 2.
- Correct big drawsWith more than 8 outs, subtract the outs above 8 from the rule-of-4 figure: 15 outs is 60 − 7 = 53%.
- Compare with the priceCall when your chance of hitting is higher than the share of the final pot your call represents (the pot odds).
Rule of 2: outs × 2 = % to hit with one card to come.
Rule of 4: outs × 4 = % to hit by the river from the flop, seeing both cards.
Correction: above 8 outs, outs × 4 − (outs − 8).
Example: you hold a flush draw on the flop and your opponent moves all-in. 9 outs × 4 = 36%; the exact figure is 35.0%. If they bet instead and you’ll face another bet on the turn, only the next card counts: 9 × 2 = 18%, exactly 19.1%.
How accurate is the rule of 2 and 4?
For small draws the rule of 4 is excellent — within a point of the exact odds up to 8 outs. Past that it overestimates more with every out, because it simply adds the turn and river chances — counting the run-outs where you’d hit on both streets twice. With 15 outs it says 60% against a true 54.1%; with 20 outs, 80% against 67.5%.
Chance to hit by the river (%), by number of outs
The rule of 2 errs the other way: one out is worth 2.1% on the flop and 2.2% on the turn, a bit more than 2%, so it slightly underestimates — by 1.6 points for a flush draw on the turn. That rarely changes a decision. Here is every draw size side by side:
Flop to river (both cards)
| Outs | × 4 | Corrected | Exact |
|---|---|---|---|
| 1 | 4% | 4% | 4.3% |
| 2 | 8% | 8% | 8.4% |
| 3 | 12% | 12% | 12.5% |
| 4 | 16% | 16% | 16.5% |
| 5 | 20% | 20% | 20.4% |
| 6 | 24% | 24% | 24.1% |
| 7 | 28% | 28% | 27.8% |
| 8 | 32% | 32% | 31.5% |
| 9 | 36% | 35% | 35.0% |
| 10 | 40% | 38% | 38.4% |
| 11 | 44% | 41% | 41.7% |
| 12 | 48% | 44% | 45.0% |
| 13 | 52% | 47% | 48.1% |
| 14 | 56% | 50% | 51.2% |
| 15 | 60% | 53% | 54.1% |
| 16 | 64% | 56% | 57.0% |
| 17 | 68% | 59% | 59.8% |
| 18 | 72% | 62% | 62.4% |
| 19 | 76% | 65% | 65.0% |
| 20 | 80% | 68% | 67.5% |
One card to come
| Outs | × 2 | Flop → turn | Turn → river |
|---|---|---|---|
| 1 | 2% | 2.1% | 2.2% |
| 2 | 4% | 4.3% | 4.3% |
| 3 | 6% | 6.4% | 6.5% |
| 4 | 8% | 8.5% | 8.7% |
| 5 | 10% | 10.6% | 10.9% |
| 6 | 12% | 12.8% | 13.0% |
| 7 | 14% | 14.9% | 15.2% |
| 8 | 16% | 17.0% | 17.4% |
| 9 | 18% | 19.1% | 19.6% |
| 10 | 20% | 21.3% | 21.7% |
| 11 | 22% | 23.4% | 23.9% |
| 12 | 24% | 25.5% | 26.1% |
| 13 | 26% | 27.7% | 28.3% |
| 14 | 28% | 29.8% | 30.4% |
| 15 | 30% | 31.9% | 32.6% |
| 16 | 32% | 34.0% | 34.8% |
| 17 | 34% | 36.2% | 37.0% |
| 18 | 36% | 38.3% | 39.1% |
| 19 | 38% | 40.4% | 41.3% |
| 20 | 40% | 42.6% | 43.5% |
Dirty outs: when an out isn’t really an out
Outs assume your hand wins when it gets there. Sometimes the card that completes your draw also completes something better for your opponent. Those are dirty outs, and they come off the count.
Take against a set, , on . You see 9 hearts, but the 2♥ pairs the board and gives the set a full house. That leaves 8 clean outs — and even when you hit on the turn, the set can still fill up on the river. The outs math says 32.7% by the river; your real equity over every run-out is 25.6%. Load “Dirty outs” in the finder above to see it card by card.
- Pairing cards against a set or two pair. Any card that pairs the board can give them a full house.
- Straight cards on a two-suited board. If your opponent has a flush draw, the straight cards of their suit complete their flush too.
- Overcards that may not be good. Pairing your ace isn’t an out if your opponent could hold a better ace.
The opposite happens too. In the flush-draw spot, against , 9 outs predict 36.4% with both hands known, while real equity is 38.0%: runner-runner cards — a nine and a ten for a straight, or an eight and a seven for two pair — win some pots the outs count ignores.
From outs to a decision
Outs only tell you how often you hit; the price tells you whether that’s enough. If you need 25% to call and your draw hits 35% by the river with no more betting, call; if you need 25% and only the next card counts, 9 outs (19.1%) falls short unless you expect to win more later. The pot odds calculator does that comparison for any bet, and the poker odds chart lists every draw.
The best practice is live hands. Deal a free table on FizzPoker and add a bot — one needs no account — or sign in to fill the table with bots at five levels. After the game, the Fizz Score reviews each graded decision you made against game-theory models and labels it acceptable, inaccuracy, mistake or blunder — an advisory second opinion on the draws you chased and the ones you let go. To check your instincts right now, take the poker test: twelve Hold’em decisions, graded.
Questions people ask
What are outs in poker?
Outs are the unseen cards that would turn your hand into the likely winner. A flush draw has 9 outs: the 13 cards of the suit minus the 4 you can already see.
What is the rule of 2 and 4?
A shortcut for turning outs into a percentage. Multiply your outs by 2 for the chance of hitting on the next card, or by 4 on the flop for the chance of hitting by the river when you will see both cards. With 9 outs that gives about 18% and 36%.
How accurate is the rule of 2 and 4?
The rule of 4 stays within one percentage point of the exact odds up to 8 outs, then overestimates: 15 outs is 54.1% exact, not 60%. Subtracting the outs above 8 fixes most of that (15 outs: 53%). The rule of 2 slightly underestimates: 9 outs on the turn is 19.6%, not 18%.
How many outs does a flush draw have?
Nine. On the flop that is a 19.1% chance to hit on the turn and 35.0% by the river if you see both cards; on the turn it is 19.6% for the river.
What are dirty outs?
Dirty outs are cards that complete your draw but also improve your opponent to an even better hand — for example a heart that pairs the board when you hold a flush draw against a set, giving them a full house. Don’t count them.
Should I multiply by 4 when I face a bet on the flop?
Only if you are all-in or sure to see both cards for this price. If there will be another bet on the turn, use the chance of hitting on the next card (outs × 2, or outs ÷ 47 exactly), because you will have to pay again to see the river.