Straight Draw Odds: Open-Ended & Gutshot Probabilities

Open-Ended Straight Draw Odds

An open-ended straight draw (OESD) is a four-card sequence that can be completed by cards on either end. Because two ranks each contribute four cards, an OESD always has exactly 8 outs. For example, holding 6♦7♦ on a board of 8♣9♠K♥ gives you a straight draw that is completed by any 5 (6-5 low end) or any 10 (10-high straight) — four 5s and four 10s, totalling 8 outs. From the flop with two cards still to come, the OESD hits 31.5% of the time. The Rule of 4 gives 8 × 4 = 32%, very close to exact. On the turn with one card remaining, the hit rate drops to 17.4% (Rule of 2: 8 × 2 = 16%). This makes the OESD one of the strongest draws in No-Limit Hold'em, closely rivalling a flush draw.

Gutshot Straight Draw Odds

A gutshot straight draw (also called an inside straight draw or belly buster) has only 4 outs because the draw contains an internal gap that only one specific rank can fill. For example, holding 6♦8♦ on a board of 5♠9♠K♥ needs a 7 — and only a 7 — to complete the straight. There are four 7s in the deck, so you have 4 outs. From the flop, a gutshot hits 16.5% of the time by the river. On the turn alone, the probability is just 8.7%. Because of this low equity, a gutshot is almost never profitable to call against a half-pot bet or larger without significant implied odds. When in doubt, fold a gutshot to a big bet on the turn.

How to Count Straight Draw Outs

The first step is identifying whether your draw is open-ended or a gutshot. An OESD has four consecutive cards with open ends — any card on either side completes a five-card straight. A gutshot has a gap in the middle requiring one specific rank. A double gutshot (double belly buster) is rarer: two separate gutshot draws exist simultaneously, each targeting a different rank. Because two ranks × four cards each = 8 outs, a double gutshot has the same equity as an OESD, but is harder to recognise at the table.

Note: Always check whether some of your outs give a straight to the board that another player might also hold. Outs that complete a straight for opponents may be “tainted” and worth discounting slightly.

When to Call with a Straight Draw

Compare your draw's equity to the pot odds required to call. If equity exceeds the pot odds percentage, calling is mathematically profitable. The table below covers both OESD and gutshot across common bet sizes. On deep stacks, implied odds can justify calls that appear −EV on raw pot odds alone — especially if your opponent will pay off large bets when you complete the straight.

Note: implied odds may justify calling when marked as −EV above, especially in deep-stacked games where completing your straight earns significant additional bets on later streets.

Straight Draws vs Flush Draws

A flush draw has 9 outs versus an OESD's 8 outs — just one extra out, which translates to roughly 3–4% more equity across both streets. In practice both are strong draws and can often be played similarly. The meaningful difference arrives at the top: a flush draw + OESD combo (15 outs) is a coin-flip against most made hands from the flop, while a gutshot is substantially weaker than either.

OESD vs Gutshot: Which Should You Play?

An OESD with 31.5% equity from the flop is strong enough to semi-bluff aggressively. You can raise or lead with an OESD as a semi-bluff: if called, you have meaningful equity to fall back on; if your opponent folds, you win the pot immediately. Fold equity makes the OESD even more +EV than the raw probability suggests. A gutshot, by contrast, has only 16.5% equity — borderline against small bets and clearly −EV against anything larger. Gutshots are best played as passive calls (when pot odds allow) rather than semi-bluff raises, because the draw equity alone rarely justifies building a large pot. The exception is a gutshot with extra equity: overcards, a backdoor flush draw, or position against a weak range can push a gutshot into profitable territory.

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