Implied Probability Calculator
Enter one price in American, decimal or fractional odds and this returns the percentage chance it represents — plus the same price written every other way. Everything runs in your browser.
- Implied probability
- 52.38%
- Breaks even at
- 52.38%
- Implied 1-in-N
- 1 in 1.91
| Format | Price |
|---|---|
| Decimal | 1.91 |
| American | -110 |
| Fractional | 10/11 |
| Probability | 52.38% |
Add the opposing price to see why a real market’s probabilities add up to more than 100%.
Decimal: probability = 1 ÷ price. American: 100 ÷ (price + 100) for a positive price, price ÷ (price + 100) for a negative one, ignoring the sign. Fractional: denominator ÷ (numerator + denominator). A price of +100 is an even-money 50%.
Informational and educational only. 18+. This tool performs arithmetic on a figure you enter; it does not recommend any outcome and makes no prediction.
Common prices, every format
Each row is one price expressed four ways. Computed by the same code the calculator runs, so the table can never disagree with the tool above it.
| Decimal | American | Fractional | Implied probability |
|---|---|---|---|
| 1.20 | -500 | 1/5 | 83.3% |
| 1.50 | -200 | 1/2 | 66.7% |
| 1.91 | -110 | 10/11 | 52.4% |
| 2.00 | +100 | 1/1 | 50.0% |
| 2.50 | +150 | 3/2 | 40.0% |
| 3.00 | +200 | 2/1 | 33.3% |
| 4.00 | +300 | 3/1 | 25.0% |
| 6.00 | +500 | 5/1 | 16.7% |
| 11.00 | +1000 | 10/1 | 9.1% |
Worked examples across all three formats are in how to convert odds to implied probability; the one-paragraph definition is in the glossary. Once you have more than one price, the numbers stop adding to 100% — that gap is the vig, and the vig calculator measures it.
Implied probability questions
- How do you convert odds to an implied probability?
- For decimal odds, divide 1 by the price: 2.50 implies 40%. For positive American odds, use 100 ÷ (odds + 100); for negative American odds, use odds ÷ (odds + 100), ignoring the sign — so −110 implies 110 ÷ 210 = 52.38%. For fractional odds, use denominator ÷ (numerator + denominator): 10/11 implies 11 ÷ 21 = 52.38%.
- What does "implied probability" actually mean?
- It is the chance an outcome would need to have for the price to be exactly fair — the break-even point. It is arithmetic on the price, not a forecast, and it is not the same as the true probability, because every real market has a margin built in on top.
- Why do the probabilities in a market add up to more than 100%?
- Because of the margin. Two outcomes priced at −110 each imply 52.38%, which totals 104.76%. The extra 4.76% is the overround. That is why a raw implied probability always overstates the real chance a little — and why removing the margin is a separate step.
- Is a shorter price always more likely to win?
- A shorter price implies a higher probability — that is what the conversion says. Whether the market is right is a different question entirely, and nothing on this page answers it.
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