Open-Ended Straight Draw (OESD)

Also known as: Open Ended Straight Draw, open-ender, up and down straight draw, double-ended straight draw

Four consecutive cards open at both ends — 8 outs, roughly 17% per street, ~31.5% by the river.

An open-ended straight draw (OESD) has four cards in sequence, completing with a card at either end — 8 outs, double the gutshot.

With the Rule of 2 and 4:

Per street: \(8 \times 2 = 16\%\). Exact: \(\dfrac{8}{47} \approx 17.0\%\).
Flop to river: \(8 \times 4 = 32\%\). Exact: about \(31.5\%\) (the linear rule slightly overcounts here).

Eight outs is a genuine semi-bluffing engine. An OESD has enough equity to check-raise flops, float, and double-barrel as a bluff that still wins a third of the time when called. Combined with overcards or a flush draw it becomes a combo draw with 12–15+ outs and can be the equity favorite against a single pair.

Mind the nut question: an OESD where you make the nuts (and ideally are hidden) carries far better implied odds than a bottom-end draw that makes a second-best straight — classic reverse implied odds territory. Discount one-ended or idiot-end draws accordingly.

Example

You hold 8♠7♠ on 9♥6♣2♦. Any 5 or T makes the straight — 8 outs, ~31.5% by the river. As a flop check-raise semi-bluff this is ideal: real equity when called, plus a backdoor spade flush draw, plus fold equity against the c-bettor's air.