Poker Equity & OddsFlush draw odds by the river
Short answer
A flush draw on the flop has 9 outs and hits by the river 35.0% of the time, or 19.1% on the turn alone. With one card to come from the turn, it's 19.6%. The rule of 4 and 2 says 36% and 18%, close enough at the table.
Odds for the common draws
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 | Outs | Next card | By the river | Rule of 4 |
|---|---|---|---|---|
| Flush draw | 9 | 19.1% | 35.0% | 36% |
| Open-ended straight draw | 8 | 17.0% | 31.5% | 32% |
| Flush draw + open-ender | 15 | 31.9% | 54.1% | 60% |
| Gutshot | 4 | 8.5% | 16.5% | 16% |
| Two overcards | 6 | 12.8% | 24.1% | 24% |
Flush draw against top pair
Your equity: 38.9% against top pair (KQ), over all 990 runouts.
Equity is a bit higher than the 35.0% hit chance, because a few runouts win without a heart, like a five and a four for two pair. That's why I trust the calculator over the outs count.
Outs to odds chart
Nine outs is one row of a longer table. The outs chart and the rule of 4 and 2 has every count from 1 to 15 outs, flop to river and turn to river, next to what the rule says.
When the rule of 4 and 2 is wrong
It overshoots with big draws. With 15 outs (a flush draw plus an open-ender, 9♥ 8♥ on 10♥ 7♥ 2♣) it says 60%, but the real chance is 54.1%. Also, not every out is clean: a card that completes your flush can also give someone a full house. Unit 2 of the course, Outs & hitting odds, has a lesson on exactly that.
Questions
What are the odds of hitting a flush draw by the river?
35.0% with 9 outs on the flop and two cards to come. That's 378 of the 1,081 possible turn and river pairs.
What are the odds of hitting a flush on the turn?
19.1% from the flop, 9 of 47 unseen cards. If you miss the turn, the river alone gives you 19.6%, 9 of 46.
Does the rule of 4 and 2 work for a flush draw?
Close enough: it says 36% against the exact 35.0%. It gets worse with more outs: with 15 it says 60%, but the real chance is 54.1%.
Should I call a half-pot bet with a flush draw?
Against one pair, usually yes. 5♥ 4♥ on K♥ 9♥ 2♣ against K♦ Q♣ has 38.9%, and a half-pot call needs 25.0%. That assumes no more betting on the turn; the pot odds cheat sheet covers the next-card view.
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.
