Poker odds, answered
Open-ended straight draw odds
An open-ended straight draw (8 outs) makes the straight 31.5% of the time from the flop to the river, 17.0% on the turn and 17.4% on the river.
Exact counts, not simulations.
How it is counted
Two ranks complete the straight, four cards each: eight outs among the 47 unseen cards. You miss when the turn is one of the 39 others and the river one of the 38 others.
Flop to river: 1 − (39 × 38) ÷ (47 × 46) One card: 8 ÷ 47 on the turn, 8 ÷ 46 on the river
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