Open-ended straight draw odds
Outs
With 8 outs, a open-ended straight draw hits on the turn 17.0% of the time and by the river 31.5% of the time when you see both cards.
- 17.4%hit on the river, from the turn
- 2.2 to 1odds against, both cards to come
- 4.9 to 1odds against, next card only
- 32%the rule of 4 estimate
- 25%equity needed to call a half-pot bet
Understanding the Draw
An open-ended straight draw offers eight outs. These are the cards that complete your sequence. As the key figures show, the chance to hit on the turn alone is lower than the combined chance of hitting by the river. If you miss the turn, the chance to hit on the river rises slightly because fewer unseen cards remain. When both cards are dealt, the combined probability is higher than either single-card chance. This reflects two opportunities to improve. The table below breaks down these probabilities and their corresponding odds against hitting. Use these figures to assess whether a call is justified based on the current pot size.
| Cards to come | Chance to hit | Odds against |
|---|---|---|
| Turn, one card | 17.0% | 4.9 to 1 |
| River, one card | 17.4% | 4.8 to 1 |
| Turn or river, both cards | 31.5% | 2.2 to 1 |
Comparing Estimates
The rule of four provides a quick estimate for two-card situations. Multiplying outs by four yields a figure slightly higher than the exact combined probability. It is also higher than the chance of hitting on the river alone. The rule of two applies when only one card remains to be dealt. Multiplying outs by two gives a result close to the actual turn probability. These shortcuts help make quick decisions. However, exact figures are more precise for calculating expected value. Always verify if the betting structure allows seeing both cards. If an opponent goes all-in, you see both cards immediately. In this case, use the combined probability. If betting continues, evaluate each street separately using the single-card figures.
Evaluating Pot Odds
Pot odds determine if a call is profitable. A half-pot bet requires specific equity to break even. Your draw’s equity depends on how many cards remain. With both cards to come, your equity exceeds the required threshold for a half-pot bet. Therefore, calling is mathematically sound when you see both cards. If only the turn remains, your equity is lower than the required equity for a half-pot bet. In this scenario, calling is less favorable unless implied odds are considered. Implied odds account for future bets you might win. Check the table above to match your situation with the correct probability. Compare your specific equity against the required threshold for each bet size. If gambling stops being fun, free help is available via support resources.
Questions
Why is the river chance higher than the turn chance?
Fewer unseen cards remain after the turn is dealt. This slightly increases the probability that one of your outs appears on the river compared to the turn.
When should I use the rule of four?
Use the rule of four when you will see both the turn and river without further betting decisions, such as when facing an all-in bet.
Is the rule of four accurate?
It provides a close approximation. The estimate is slightly higher than the exact mathematical probability, making it a useful quick check for most situations.
Does position affect these odds?
No. The mathematical probability of hitting your draw depends only on the number of outs and cards remaining, not on your position at the table.
Every figure on this page is computed by code from a standard 52-card deck, counting every possible card and checking the count a second way. See the methodology.