Implied Probability Calculator
Convert decimal, fractional, or American odds to their implied probability. Compare with your own assessment to identify potential value bets.
Fractional: denominator ÷ (numerator + denominator) × 100
American+: 100 ÷ (odds + 100) × 100
American-: |odds| ÷ (|odds| + 100) × 100
Understanding Implied Probability
Every set of odds implies a certain probability. Bookmakers set odds to reflect their estimated chances, plus their margin (overround).
Quick Reference
| Decimal | Probability | Description |
|---|---|---|
| 1.50 | 66.67% | Strong favorite |
| 2.00 | 50.00% | Even money |
| 3.00 | 33.33% | Underdog |
| 5.00 | 20.00% | Long shot |
| 10.00 | 10.00% | Very unlikely |
Finding Value
If you believe a team has a 50% chance of winning, but the odds imply only 40%, that's a value bet. The implied probability is lower than your estimated probability.
Stripping the Margin Out
The probability implied by a price isn't the bookmaker's honest view. It includes their margin, so it always overstates the real chance. Add up the implied probabilities for every outcome in a market and you'll get more than 100%, and the excess is the margin baked into the prices.
Getting to a Fair Estimate
To approximate a fair probability, divide each outcome's implied probability by the total for the market. If two sides imply 52.4% each, the total is 104.8%, and normalizing gives 50% each. That normalized figure is closer to what the market actually thinks, and it's the number worth comparing against your own estimate.
Using It Across Books
Implied probability is also the cleanest way to compare prices from different sources, since decimal, fractional and American odds all convert to the same scale. Two prices that look similar in fractional form can differ by a full percentage point of implied probability, and over a season those small gaps decide whether an approach makes money.