Odds to Probability Converter

About this calculator

Betting odds are usually presented in one of three formats, and each converts to an implied probability differently. For decimal odds, probability = 1 ÷ decimal odds (e.g. 2.50 → 40%). For fractional odds a/b, probability = b ÷ (a+b) (e.g. 5/2 → 2/7 ≈ 28.6%). For American odds, negative numbers (favorites) use probability = (−odds) ÷ ((−odds) + 100), while positive numbers (underdogs) use probability = 100 ÷ (odds + 100).

This calculator takes an odds value in any of those formats and returns the implied probability a bookmaker's price represents. Sports bettors use it to spot value by comparing implied probability against their own estimate of the true chance of an outcome, while oddsmakers and traders use the same math to build a book and check how much margin (overround) is baked into a set of prices.