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Quick Answer — What Are My Odds of Completing a Draw?
The exact probability of hitting at least one of your outs is a hypergeometric calculation: 1 − (ways to miss every out ÷ total ways the remaining cards could come). This is more precise than the well-known 'rule of 4 and 2' (outs × 4 with two cards to come, outs × 2 with one card to come), which is a fast mental shortcut, not exact math.
Quick reference (probability of hitting, with two cards to come from a standard 47-card unseen deck):
- 4 outs (gutshot straight draw) → 16.5% exact (rule of thumb: 16%)
- 8 outs (open-ended straight draw) → 31.5% exact (rule of thumb: 32%)
- 9 outs (flush draw) → 35.0% exact (rule of thumb: 36%)
- 15 outs (combo draw, e.g. flush + straight) → 54.1% exact (rule of thumb: 60% — this is where the shortcut breaks down noticeably)
The rule of thumb tracks the exact math closely for small out counts but overstates your real probability as outs climb past about 8-9, which is exactly why this calculator computes the real combinatorial answer instead of the approximation.