Betting Margin (Overround) Calculator
Enter the odds for every outcome of a market to see the bookmaker's margin and the fair, margin-free prices.
Odds are entered in decimal format. Use the odds converter for American or fractional prices. Results are estimates for planning, not advice.
How it works
Convert each price to an implied probability (1 ÷ decimal odds) and add them up. In a fair market the total would be exactly 100%. Anything above that is the overround: the bookmaker's built-in margin. The payout rate is 100 divided by that total.
Worked example
A football match priced 2.10 / 3.40 / 3.60 adds up to 47.6% + 29.4% + 27.8% = 104.8%. The margin is 4.8% and the payout rate about 95.4%. The fair prices would be 2.20 / 3.56 / 3.77.
How to use it
Compare the same match at two sportsbooks: the one with the lower margin is giving you a better deal, whatever the headline bonus says. Margins are usually lowest on top-league match odds and much higher on props and same-game parlays.