An open-ended straight draw (OESD) is four cards in a row that a card at either end completes, such as 9-8 on a 7-6-2 flop, where any five or ten makes a straight. With four of each rank available, that is 8 outs.
Open-ended straight draw odds
| Draw | Outs | Flop to turn | Turn to river | Flop to river |
|---|---|---|---|---|
| Open-ended straight draw | 8 | 17.0% | 17.4% | 31.5% |
| Gutshot (for comparison) | 4 | 8.5% | 8.7% | 16.5% |
From the flop you hit on the turn 17.0% of the time (4.9 to 1 against) and by the river 31.5% of the time (2.2 to 1 against). That makes an open-ender almost exactly twice as likely to complete as a gutshot.
The maths behind the 8 outs
There are 47 unseen cards after the flop. Eight of them complete the straight, so the turn hits 8 ÷ 47 of the time. The chance of missing both the turn and river is 39/47 × 38/46, and one minus that gives the 31.5% figure. The rule of 2 and 4 estimates 16% and 32%, close enough to use at the table.
Calling with an open-ender
Facing a half-pot bet you need 25% equity, and facing a pot-sized bet 33.3%. With one card to come the draw has 17.0%, so it relies on implied odds. In a $100 pot facing a $50 bet, you need to win about $94 more on later streets when you hit to make the call break even.
Straights are often well hidden, which helps you get paid. When the board is three to a flush, though, the straight card can also complete someone's flush.
When to count fewer than 8 outs
- The ignorant end. If you hold 5-4 on a 7-6-2 board, an eight gives you a straight but a nine-ten would beat it. Low-end draws are worth less.
- Flush boards. If two of the board cards share a suit, two of your outs may give an opponent a flush.
- Paired boards. A full house can already be out there, or come in on the same card.
Turning the draw into a weapon
Like flush draws, open-enders make good semi-bluffs: you win immediately when your opponent folds and still have 31.5% to improve when you are all-in on the flop. Combine one with a flush draw and you have 15 outs, covered in combo draw odds.
Check any draw on the poker outs chart and test the call with the pot odds calculator.