Implied Probability Calculator — Odds to Probability
Every set of betting odds contains a probability — and a hidden bookmaker margin. Enter American, decimal or fractional odds (for one or two outcomes) to get the implied probability, the market overround (vig), and the true fair-value probabilities after removing the margin.
Odds format
Probability baked into the odds, including the bookmaker margin
- 1
Decimal odds
100 ÷ 110 + 1 = 1.9091 - 2
Implied probability
1 ÷ 1.9091 × 100 = 52.38Percentage chance implied by the odds, including bookmaker margin.
How does this calculator work?
Implied probability = 1 ÷ decimal odds × 100 (or |odds| ÷ (|odds| + 100) for American negatives). The market overround (vig) is the sum of the implied probabilities of both outcomes minus 100%. No-vig true probabilities are found by dividing each implied probability by the overround.
Formula
How this is calculated
Bookmakers express their opinion on event likelihood through odds, but they always set odds so that the combined implied probabilities of all outcomes sum to more than 100%. That excess — the overround or vig — is their built-in profit margin. For a typical two-way market at −110 / −110 (American odds), each side implies a 52.4% chance, summing to 104.8% — a 4.8% overround.
This calculator first converts any odds format to decimal (the universal form), then computes implied probability as 1 ÷ decimal odds × 100. If you enter odds for both outcomes, it shows the total overround and the "true" or no-vig probabilities — found by dividing each implied probability by the overround sum, then multiplying by 100, so they sum to exactly 100%.
The no-vig probability is what a fair market would offer; comparing it to the odds you are offered tells you whether you have an edge. This calculator treats the two-outcome case only (win/lose, over/under); for markets with a draw or more than two outcomes, each leg must be assessed individually.
Frequently asked questions
Implied probability is the bookmaker assessment of how likely an outcome is, expressed as a percentage from their odds. At −110 (American) or 1.909 (decimal), the implied probability is 52.38%. Odds shorter than true probability represent a losing bet in the long run.
Vig (vigorish) is the bookmaker margin — the sum of implied probabilities across all outcomes minus 100%. A 5% overround means the bookmaker takes about 5 cents from every dollar wagered on that market over the long run. Removing the vig gives you fair-value probabilities to assess whether your belief about an outcome exceeds the bookmaker implied probability.
For fractional odds N/D (e.g. 4/5), the decimal equivalent is N/D + 1, so 4/5 + 1 = 1.80. The implied probability is 1 ÷ 1.80 = 55.6%. This calculator does the conversion automatically.
Also known as
TG we-Calculate Editorial Team. (2026). Implied Probability Calculator — Odds to Probability [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/implied-probability-calculator
TG we-Calculate Editorial Team. "Implied Probability Calculator — Odds to Probability." TG we-Calculate. 2026. https://we-calculate.com/calculator/implied-probability-calculator.
TG we-Calculate Editorial Team, "Implied Probability Calculator — Odds to Probability," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/implied-probability-calculator
@misc{wecalculate_implied_probability_calculator, title = {Implied Probability Calculator — Odds to Probability}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/implied-probability-calculator}}, year = {2026}, note = {TG we-Calculate} }
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