Poker Odds Calculator
This calculator answers three separate questions poker players run into at the table: how likely a draw is to complete, whether the price being offered is worth calling, and what a given betting line actually means as a probability. For outs, you enter your out count and the street; it returns the exact probability of hitting by the river, worked out from the deck rather than the rule-of-2-and-4 shortcut, with that shortcut shown next to it so the gap is visible. For pot odds, you enter the pot size and the amount to call; it returns the ratio and the break-even percentage you need to show a profit. It then measures your equity against that break-even number and tells you whether calling is profitable, in chips.
Should you call? Outs, equity and pot odds
| Your equity (exact) | — |
|---|---|
| Rule of 2 and 4 estimate | — |
| Break-even equity you need | — |
| Pot odds | — |
| Expected value of calling | — |
Betting odds to implied probability
| American | — |
|---|---|
| Decimal | — |
| Fractional (approx.) | — |
Turning outs into an exact probability
After the flop, two cards are still to come and 47 cards are unseen, so the calculator counts every possible two-card combination from what's left in the deck and checks how many of them contain at least one out. Divide that count by the total number of two-card combinations and you get the true probability of hitting by the river. After the turn, only one card remains, so the math simplifies to outs divided by 46 unseen cards, since there's nothing left to combine.
For a flush draw with 9 outs and two cards to come, this gives 35.0% by the river. Reach the turn with the same nine outs still live and your one-card equity for the river alone is 19.6%, a different figure from the flop number because there's only one draw left instead of two. Mixing these two numbers up, or applying the flop percentage on the turn, is one of the more common arithmetic mistakes players make away from a calculator, and it tends to make marginal turn calls look better than they are.
Where the rule of 2 and 4 breaks down
The rule of 2 and 4 multiplies your outs by 4 on the flop and by 2 on the turn as a mental shortcut, and it's close enough for small draws where speed matters more than precision. It stops being close once the out count climbs. At 15 outs on the flop, the rule says 60%; the actual figure, computed from the 47 unseen cards, is 54.1%, a gap of almost six points. At 20 outs the rule says 80% against a true 67.5%, off by 12.5 points. The shortcut consistently overestimates equity for big combination draws on the flop, and the error grows roughly in step with the out count.
On the turn the error runs the other way. The rule of 2 understates a 9-out draw as 18% when the real one-card figure is 19.6%, and the gap widens slightly as outs increase. Neither error is large enough to flip a clearly profitable or clearly losing decision, but both matter on the close ones, which is exactly where a rough mental shortcut is usually being leaned on hardest.
Pot odds, break-even percentage and the call/fold verdict
Pot odds compare what's already in the pot to what it costs to continue, expressed as a ratio. If there's 100 in the pot and you must call 20 to stay in the hand, the pot odds are 5 to 1. To turn that ratio into the equity you need just to break even, divide the call by the total of the pot plus the call: 20 divided by 120 is 16.7%. Win more often than that and calling shows a long-run profit; win less and it's a loser regardless of how any single hand turns out.
The calculator sets your outs-based equity against this break-even figure and states the verdict directly rather than leaving you to do the comparison. With the 9-out flush draw from above at 35.0% equity against a 16.7% break-even requirement, calling is profitable by roughly 22 chips in expectation on that 100 pot. The EV is worked out as equity times the total pot after the call, minus the cost of the call itself, so it scales with both your stack and the size of the bet you're facing.
American, decimal and fractional odds explained
Betting odds and poker equity are the same underlying idea expressed in different notations, and the converter section handles all three formats a bettor is likely to run into. Decimal odds convert to implied probability as 1 divided by the decimal figure, so 2.50 implies 40%. Fractional odds of a/b convert as b divided by (a+b), so 3/2 also works out to 40%, matching the decimal example because they describe the same price. American odds split into two cases: positive odds convert as 100 divided by (odds plus 100), so +150 implies 40%; negative odds convert as the absolute value of the odds divided by (absolute odds plus 100), so -110 implies 52.4%.
These conversions are exact arithmetic, not estimates, which is the same standard the outs calculation is held to elsewhere on this page. There's no rounding shortcut hiding in either one.
The bookmaker's overround
Implied probability on its own doesn't tell you what a bookmaker actually expects to happen, because a real market's prices almost always add up to more than 100%. That excess is the overround, also called the vig or the margin, and it's the house's structural edge built into the price rather than a reflection of the true chances. Two sides of a market both priced at -110 each imply 52.4%, and the two together sum to 104.8%, a 4.8-point overround. The bookmaker collects roughly that margin on balanced action regardless of which side actually wins.
This matters for anyone comparing a sportsbook line to a poker-style equity number: the sportsbook figure already has the house cut baked into it, while the outs-based equity above does not, since a deck of cards has no vig to extract.
What this calculator doesn't do
It's worth being direct about scope. The outs-to-equity figure assumes your outs are genuinely live and doesn't discount them for cards an opponent might already be holding, so a range-aware equity tool will sometimes land on a different number for the same draw. It doesn't model multi-way pots, where additional opponents change the math beyond a simple outs count. It doesn't factor in implied odds, meaning future bets you might win or lose on later streets, only the price you're facing right now. And the odds converter is pure arithmetic on the number you type in; it doesn't shop lines across books or check whether a given price is actually the best one available.
Inside those boundaries, every figure the tool returns is exact rather than estimated, and that's a deliberate trade: fewer assumptions, in exchange for numbers you can check by hand if you want to.
Frequently Asked Questions
What does this poker odds calculator actually compute?
It computes three things: the exact probability of completing your draw by the river based on your outs and the current street, the break-even percentage implied by your pot odds, and whether calling is profitable given both. It also converts American, decimal and fractional betting odds to implied probability.
How is the outs-based equity different from the rule of 4?
The rule of 4 multiplies outs by 4 as a fast mental estimate. This calculator instead counts the actual combinations of unseen cards, so a 15-out draw on the flop shows as 54.1% rather than the rule's 60%, and a 20-out draw shows 67.5% rather than 80%.
What are pot odds and how do you calculate them?
Pot odds are the ratio of the current pot to the cost of a call. With a pot of 100 and a call of 20, that's 5 to 1. Converted to a percentage you need to win to break even, it's call divided by pot-plus-call: 20 divided by 120, or 16.7%.
How do I know if a call is profitable?
Compare your equity from the outs calculation against the break-even percentage from your pot odds. If equity is higher, the call shows a long-run profit; if lower, it's a loser. The tool also states the expected value in chips, calculated as equity times pot-plus-call, minus the call.
How do you convert American odds to a probability?
Positive American odds convert as 100 divided by (odds plus 100), so +150 implies 40%. Negative American odds convert as the odds' absolute value divided by (absolute value plus 100), so -110 implies 52.4%. Decimal odds convert as 1 divided by the decimal figure, and fractional odds a/b as b/(a+b).
What is the bookmaker's overround?
The overround is the amount by which a market's implied probabilities exceed 100% once every outcome is priced. Two -110 sides of the same market imply 52.4% each, summing to 104.8%, a 4.8-point overround that represents the bookmaker's built-in structural edge on that market.
Why do outs count differently after the flop than after the turn?
After the flop, 47 cards are unseen and two more will be dealt, so equity is based on two-card combinations from that unseen set. After the turn, only 46 cards are unseen and just one more card comes, so equity simplifies to outs divided by 46, a single-card calculation.
Does the calculator account for opponent ranges or implied odds?
No. It treats your entered outs as fully live and calculates pure card-removal probability, without discounting for cards an opponent might hold or factoring in bets you could win or lose on later streets. Those require range-based equity tools, which is a separate, more assumption-heavy calculation.
Can I use this tool for sports betting odds instead of poker?
Yes, the odds converter works independently of the poker side of the calculator. Enter American, decimal or fractional odds and it returns the implied probability using the same arithmetic bookmakers use to set lines, which is useful for comparing prices quoted in different formats across two different books.