Outs
The cards left in the deck that turn your hand into the winner. Counting them gives you your chance to improve: each out is worth ~4% on the flop and ~2% on the turn.
An out is any card that completes your hand. With J♥T♠ on a 9♣8♦2♠ flop you have an open-ended straight draw: any Q or any 7 gets you there — 8 outs.
What outs are worth (exact numbers from the engine)
Enumerating every possible runout:
| Draw | Outs | Complete by the river (from the flop) |
|---|---|---|
| Flush (four to a suit) | 9 | 35.0% |
| Open-ended straight draw | 8 | 31.5% |
| Gutshot straight draw | 4 | 16.5% |
From the turn, with just one card to come, the flush drops to 19.6%.
The rule of 4 and 2
The table shortcut: outs × 4 ≈ your chance to complete from the flop; outs × 2 ≈ from the turn. For the flush: 9 × 4 = 36% (real: 35.0%) and 9 × 2 = 18% (real: 19.6%). Accurate enough to decide in seconds.
The catch: dirty outs
Not every out wins the hand. If the card that completes your straight also gives someone a flush, that out is “dirty” and worth less. That’s why counting outs is step one, and comparing them against your pot odds is step two — the outs calculator does both by exact enumeration, no approximation rule needed.