Fractional Odds Probability Calculator

Translating traditional odds format into probability

Fractional odds like "5 to 1," common in horse racing and traditional UK bookmaking, express profit won per unit staked rather than probability directly - converting to implied probability makes it possible to compare against decimal or moneyline odds on the same scale.

Worked example

For odds of 5 to 1:

Implied Probability = 1 / (5 + 1) x 100 = 16.67%

This confirms the standard interpretation of "5 to 1 odds against" - a roughly 1-in-6 chance of that outcome occurring, according to the odds as quoted (before removing any bookmaker margin, which requires odds from both/all sides of the market to calculate).