--- title: "20 Outs on the Flop: Odds to Hit" url: "https://georgelipoker.com/outs/20-outs-flop.md" canonical_url: "https://georgelipoker.com/outs/20-outs-flop" last_updated: "2026-10-20" type: "reference" summary: "67.53% by the river with 20 outs on the flop. The exact figure, the odds against and which pot-fraction bets are worth calling." related: ["https://georgelipoker.com/outs.md"] --- # 20 Outs on the Flop: Odds to Hit 67.53% by the river with 20 outs on the flop. The exact figure, the odds against and which pot-fraction bets are worth calling. 67.53% is the exact chance by the river when you count 20 outs on the flop. Read on for the odds against, the shortcut figure and a full table of bet sizes with a call or fold verdict. - Chance to hit by the river: 67.53% (20 outs, two cards to come) - Chance on the next card: 42.55% - Odds against by the river: 0.48 : 1 - Rule of 4 estimate: 80% (+12.47 points from the exact chance) ## The count behind 20 outs on the flop Counts this high behave differently. At 67.53%, the equity a call needs is below your chance for most bet sizes, and sometimes for all of them. - Unseen cards: 47 - Your outs: 20 - Cards that miss: 27 - Pairs of cards with no out: 351 - Pairs with at least one out: 730 - Chance by the river: 67.53% - Chance on the next card: 42.55% - Odds against hitting: 0.48 : 1 - Estimate from the rule of 4: 80% - Error of the rule of 4: +12.47 points - Adjusted rule 4k - (k - 8): 68% - Error of the adjusted rule: +0.47 points - Chance by the river = 1 - C(u - k, 2) / C(u, 2), with u = 47 unseen cards - For 20 outs: 1 - C(27, 2) / C(47, 2) = 1 - 351 / 1,081 = 67.53% - Next card = 20 / 47 = 42.55% Count the ways to miss twice: 27 cards miss, and 351 pairs can be drawn from them. Take that from 1,081 pairs in all and 730 are left, so 67.53% of the run-outs help you. Rounding in your head to 80% would flatter the draw by 12.47 points. With 20 outs, that gap is big enough to flip a close call. Take off the outs above 8 and the flop rule becomes 68%, an error of +0.47 points. That is a much better stand-in than 80%. ## Which holding has 20 outs? No single common draw has exactly 20 outs. A count like this comes from combining draws and removing the cards that count twice. Not every out is clean. Here is the chance once shared outs are removed: from 67.53% down to 59.76% when 3 are shared. 20 outs on the flop when some outs are shared with a better hand | Shared outs | Effective outs | Chance by the river | Chance given up | | --- | --- | --- | --- | | 0 | 20 | 67.53% | 0.00 points | | 1 | 19 | 65.03% | 2.50 points | | 2 | 18 | 62.44% | 5.09 points | | 3 | 17 | 59.76% | 7.77 points | ## The bets 20 outs can call on the flop Here is the price list. For each bet size it shows the equity a call needs, your margin over it and the verdict, and every verdict is Call. 20 outs on the flop against every bet size, with your chance by the river at 67.53% | Bet size | Equity a call needs | Margin over it | Verdict | | --- | --- | --- | --- | | 1/4 pot | 16.67% | +50.86 points | Call | | [1/3 pot](https://georgelipoker.com/call-or-fold/20-outs-flop-vs-third-pot.md) | 20.00% | +47.53 points | Call | | 2/5 pot | 22.22% | +45.31 points | Call | | [1/2 pot](https://georgelipoker.com/call-or-fold/20-outs-flop-vs-half-pot.md) | 25.00% | +42.53 points | Call | | [2/3 pot](https://georgelipoker.com/call-or-fold/20-outs-flop-vs-two-thirds-pot.md) | 28.57% | +38.96 points | Call | | [3/4 pot](https://georgelipoker.com/call-or-fold/20-outs-flop-vs-three-quarter-pot.md) | 30.00% | +37.53 points | Call | | [full pot](https://georgelipoker.com/call-or-fold/20-outs-flop-vs-pot-size.md) | 33.33% | +34.20 points | Call | | 1.25x pot | 35.71% | +31.82 points | Call | | 1.5x pot | 37.50% | +30.03 points | Call | | 2x pot | 40.00% | +27.53 points | Call | | 3x pot | 42.86% | +24.67 points | Call | | 4x pot | 44.44% | +23.09 points | Call | Your chance of 67.53% is at least one half, so no bet size is too big: any size is a call, because the equity a call needs never reaches 50%. ## Nearby counts on both streets Neighboring counts help you judge a close draw. One out more or less shifts the chance by roughly 2.50 points on this street. Counts near 20: the chance by the river on the flop and on the turn | Outs | Flop, by the river | Turn, by the river | | --- | --- | --- | | [18](https://georgelipoker.com/outs/18-outs-flop.md) | 62.44% | 39.13% | | [19](https://georgelipoker.com/outs/19-outs-flop.md) | 65.03% | 41.30% | | 20 (this page) | 67.53% | 43.48% | - [20 outs on the turn](https://georgelipoker.com/outs/20-outs-turn.md): 43.48% on the river. - [19 outs on the flop](https://georgelipoker.com/outs/19-outs-flop.md): 65.03% by the river. ## When a bet buys only one card Facing a half-pot bet, compare 25.00% with 42.55% when you will pay again on the turn. A margin of +17.55 points says Call, while the two-card view gave +42.53 points. Drop to the next-card chance and the number of calls goes from 12 to 10 out of 12. ## Questions ### How good is a draw with 20 outs on the flop? With 20 outs on the flop you hit by the river 67.53% of the time, about 68 of every 100 hands, and on the next card 42.55%. The odds against hitting by the river are 0.48 : 1, since 351 of 1,081 pairs of unseen cards hold no out. ### What does the rule of 4 say for a count of 20? The rule of 4 gives 80% for 20 outs against an exact 67.53%, an error of +12.47 points, so it overstates the draw. The adjusted rule 4k - (k - 8) gives 68%, an error of +0.47 points, and is the closer figure. ### Which bets can 20 outs call on the flop? At 67.53% by the river, you can call all 12 bet sizes. A half-pot bet needs 25.00%, a margin of +42.53 points, so against half the pot the verdict is Call. Any bet size is a call, because 67.53% is above one half. ### What is the effective count if some of the 20 outs are shared? Take them off the count first. With one shared out the chance by the river falls from 67.53% to 65.03%, and with 3 shared it falls to 59.76%, a loss of 7.77 points. The effective count is then 17 outs. ## How this is computed The chance to hit by the river from the flop is 1 - C(u - k, 2) / C(u, 2), where u = 47 unseen cards and k is your effective outs. For 20 outs that is 1 - 351 / 1,081 = 67.53%. The chance on the next card is k / 47, here 42.55%. The rule of 4 figure is 4 x k, here 80%, and its error is that figure minus the exact chance in percentage points, here +12.47 points. The adjusted rule 4k - (k - 8) gives 68%, an error of +0.47 points. Seen as a pure card count, the 47 unseen cards are all equally likely and an opponent's hand removes none of them. Prices use a $100 pot and a call equal to the bet, so the equity needed is the bet over the pot plus two bets. Computed from the closed form by the GeorgeLiPoker math library. ## Related pages - [Outs calculator](https://georgelipoker.com/tools/outs-calculator.md): Enter your own count and street. - [Pot odds calculator](https://georgelipoker.com/tools/pot-odds-calculator.md): Enter a pot and a bet to see the equity a call needs. - [Outs and odds to hit](https://georgelipoker.com/outs.md): The chance to hit for every count on both streets. - [20 outs on the turn](https://georgelipoker.com/outs/20-outs-turn.md): The same count with one card to come. - [Pot odds for a 1.5x-pot bet](https://georgelipoker.com/pot-odds/1-5x-pot.md): The equity a 1.5x-pot call needs. - [Pot odds for a third-pot bet](https://georgelipoker.com/pot-odds/third-pot.md): The equity a third-pot call needs. - [Hand equity](https://georgelipoker.com/equity.md): Your chance to win against a named hand. ## Related - [Outs and Odds to Hit by Street](https://georgelipoker.com/outs.md)