Pot odds compare the cost of a call with the pot a player can win. Required equity = call ÷ (pot after the bet + call). If a hand wins more often than that percentage, calling is profitable on that bet alone. A $50 call into a $150 pot needs 25% equity. All numbers below were computed with a Python script.
How are pot odds and required equity calculated?
Pot odds are written as a ratio or a percentage. Using the same example, the pot is $150 after the opponent bets $50, so the player is offered 3-to-1 ($150 ÷ $50). The equivalent required equity is $50 ÷ ($150 + $50) = 25%. The two forms always agree: required equity = 1 ÷ (ratio + 1).
How is equity estimated from outs?
Outs are unseen cards that improve a hand to a likely winner. With a hole-card pair and a three-card flop, 47 cards are unseen. Exact equity with two cards to come is 1 − C(47−outs, 2) ÷ C(47, 2). With one card to come on the turn, 46 cards are unseen, so equity is outs ÷ 46.
Two shortcuts approximate this. The rule of 4 multiplies outs by 4 on the flop, and the rule of 2 multiplies outs by 2 on the turn.
| Outs | Rule of 4 (flop) | Exact, flop to river | Rule of 2 (turn) | Exact, turn to river |
|---|---|---|---|---|
| 2 | 8% | 8.4% | 4% | 4.3% |
| 4 (gutshot) | 16% | 16.5% | 8% | 8.7% |
| 6 | 24% | 24.1% | 12% | 13.0% |
| 8 (open-ended straight draw) | 32% | 31.5% | 16% | 17.4% |
| 9 (flush draw) | 36% | 35.0% | 18% | 19.6% |
| 12 | 48% | 45.0% | 24% | 26.1% |
| 15 | 60% | 54.1% | 30% | 32.6% |
Exact values calculated with Python (math.comb) for this guide. Assumes every out is clean and the opponent’s cards are unknown.
When does the rule of 4 stop working?
The table shows the rule of 4 is within about 1 point for up to 9 outs. At 12 outs it overstates equity by 3 points (48% versus 45.0%), and at 15 outs by almost 6 points (60% versus 54.1%). Players with large draws can use 4 × outs minus a few points, or the exact figure from the table.
What do four worked examples look like?
Example 1: flush draw on the flop. The pot is $100 and the opponent bets $50, making the pot $150. The call is $50, so required equity is 50 ÷ 200 = 25%. A flush draw has 9 outs and 35.0% exact equity with two cards to come. The call clears the threshold, assuming the player sees both cards without facing another bet.
Example 2: open-ended straight draw on the turn. The pot is $60 and the opponent bets $40, making the pot $100. The call is $40, so required equity is 40 ÷ 140 = 28.6%. Eight outs give 8 ÷ 46 = 17.4%. The direct price is too high, so the call needs extra expected winnings on later streets to be profitable.
Example 3: gutshot on the turn with implied odds. The pot is $90 and the opponent bets $30, making the pot $120. The call is $30, so required equity is 30 ÷ 150 = 20.0%. Four outs give 4 ÷ 46 = 8.7%. Break-even needs implied winnings X where 30 ÷ (150 + X) = 0.087, so X = $195. That is much more than the pot, which makes the call unlikely to pay off without a very deep stack.
Example 4: combination draw on the flop. The pot is $80 and the opponent bets $60, making the pot $140. The call is $60, so required equity is 60 ÷ 200 = 30.0%. A flush draw combined with an open-ended straight draw has 15 outs (9 + 8 − 2 shared), which is 54.1% exactly. The call is comfortably profitable on pot odds, and a raise may also be worth considering.
What do pot odds leave out?
Pot odds treat equity as if the hand were checked to the river. In practice, later bets, folds, and position change the real value. Implied odds add money won on future streets, and reverse implied odds subtract money lost when a made hand loses to a better one. Outs can also be dirty when a completing card gives the opponent an even stronger hand. This guide counts all outs as clean.
More decision frameworks sit in the poker strategy hub. Tournament players can apply the same arithmetic alongside stack-size concepts covered in the tournament section. The same arithmetic applies to live events such as those in the WSOP section, and to cost comparisons across poker sites, where rake sets the price of each decision.
Where can players find help with gambling problems?
Poker involves financial risk and is not suitable for everyone. Players who feel gambling is becoming a problem can call or text the National Problem Gambling Helpline at 1-800-MY-RESET (1-800-697-3738); the National Council on Problem Gambling (NCPG) also lists 1-800-522-4700 as still active. More information is at ncpgambling.org. Only wager money that can be lost. Players must be of legal age in their state.
Verified on October 20, 2026.
