Poker Equity & OddsOuts chart and the rule of 4 and 2
Short answer
Count the cards that finish your hand, then multiply by 4 on the flop or by 2 on the turn. Nine outs say 36%; the exact flop-to-river figure is 35.0%. The shortcut gets worse above about 12 outs: 15 outs say 60%, the real number is 54.1%. Every figure here is counted by the Poker Equity & Odds engine.
How many outs does my draw have?
Each row is a real hand on a real flop. The app's Outs tool counted the outs, and the chances count every unseen card.
| Draw on the flop | Example | Outs | Next card | By the river | Rule of 4 |
|---|---|---|---|---|---|
| Flush draw | 5♥ 4♥ on K♥ 9♥ 2♣ | 9 | 19.1% | 35.0% | 36% |
| Open-ended straight draw | 5♣ 4♣ on 7♦ 6♠ 2♥ | 8 | 17.0% | 31.5% | 32% |
| Flush draw + open-ender | 9♥ 8♥ on 10♥ 7♥ 2♣ | 15 | 31.9% | 54.1% | 60% |
| Gutshot | 9♣ 8♦ on J♥ 7♠ 2♣ | 4 | 8.5% | 16.5% | 16% |
| Two overcards | A♣ K♦ on 8♥ 6♠ 2♣ | 6 | 12.8% | 24.1% | 24% |
The rule of 4 and 2 in two steps
- Count the outsEvery unseen card that makes your hand the best hand. A flush draw on the flop has 9: the hearts you can't see.
- MultiplyTwo cards to come: outs times 4. One card to come: outs times 2. Nine outs on the flop says 36%. Counted, it's 35.0%.
Four on the flop, two on the turn.
Full outs chart, 1 to 15
| Outs | Flop to river | Rule of 4 | Turn to river | Rule of 2 |
|---|---|---|---|---|
| 1 | 4.3% | 4% | 2.2% | 2% |
| 2 | 8.4% | 8% | 4.3% | 4% |
| 3 | 12.5% | 12% | 6.5% | 6% |
| 4 | 16.5% | 16% | 8.7% | 8% |
| 5 | 20.4% | 20% | 10.9% | 10% |
| 6 | 24.1% | 24% | 13.0% | 12% |
| 7 | 27.8% | 28% | 15.2% | 14% |
| 8 | 31.5% | 32% | 17.4% | 16% |
| 9 | 35.0% | 36% | 19.6% | 18% |
| 10 | 38.4% | 40% | 21.7% | 20% |
| 11 | 41.7% | 44% | 23.9% | 22% |
| 12 | 45.0% | 48% | 26.1% | 24% |
| 13 | 48.1% | 52% | 28.3% | 26% |
| 14 | 51.2% | 56% | 30.4% | 28% |
| 15 | 54.1% | 60% | 32.6% | 30% |
When the rule is wrong
9 outs, flop to river
Rule of 4 says 36%. Close enough at the table.
15 outs, flop to river
Rule of 4 says 60%. Six points too high.
The rule adds the turn's chance and the river's chance as if they were separate. They aren't: when the turn hits, the river doesn't need to. With a few outs the overlap is small. With 15 outs, a flush draw plus an open-ender like 9♥ 8♥ on 10♥ 7♥ 2♣, the overlap is big and the rule overshoots by six points. Above about 12 outs, take a few points off, or read the chart.
Outs that don't win
A heart that pairs the board can fill a full house for a player holding a set. The flush comes in and still loses. The Outs tool greys those cards out and counts the rest.
Two overcards are 6 outs only when their hand holds none of your ranks. Against two pair, hitting your ace makes a pair that is still behind. Count fewer.
Unit 2 of the course, Outs & hitting odds, spends two lessons on exactly this: Outs that don't win, and Overcards aren't always outs.
Tap in the board, get the outs
Outs & Odds lists the cards that win, the rule's guess and the exact chance side by side. Free, and it works offline.
Questions
What is the rule of 4 and 2?
A table shortcut: outs times 4 with two cards to come, outs times 2 with one. Nine outs on the flop gives 36%, close to the exact 35.0%.
How many outs does an open-ended straight draw have?
Eight: four cards at each end. 5♣ 4♣ on 7♦ 6♠ 2♥ hits by the river 31.5% of the time, 17.0% on the next card.
How accurate is the rule of 4?
Within a point up to 8 outs, two points at 10 to 11, and six points off at 15, where it says 60% against the exact 54.1%.
Do I use 46 or 47 cards?
On the flop you can't see 47 cards (52 minus your 2 and the 3 on the board). On the turn it's 46. The chart's turn column divides by 46.
Where the numbers come from. Every figure on this page comes from the app's own engine, the code that runs on your phone. Outs come from the Outs & Odds tool, hit chances are exact counts, and equities count every runout with no sampling. Engine build 18a5e00d. More worked numbers: flush draw odds and the pot odds cheat sheet.