Work out bookmaker margin instantly with clear inputs, formula shown and shareable results.
The book total is the sum of one over each price; margin is one minus the reciprocal of that total, and fair odds are each price multiplied by the book total. A 5% margin means the market pays back only 95 units per 100 staked over time, which is the hurdle every betting strategy has to clear before it can win.
Book total
book = 1 / odds A + 1 / odds B + 1 / odds C
Margin
margin = 1 - 1 / book total
book = 1 / odds A + 1 / odds B + 1 / odds C. The book total is the sum of one over each price; margin is one minus the reciprocal of that total, and fair odds are each price multiplied by the book total.
A 5% margin means the market pays back only 95 units per 100 staked over time, which is the hurdle every betting strategy has to clear before it can win.
Enter odds on outcome a, odds on outcome b, odds on outcome c (0 if none). The defaults shown are a realistic worked example — swap in your own figures to get a result you can use.