How to measure a margin
- Choose the market size2 outcomes for over/under, both teams to score or a tennis match; 3 for a 1X2 football market.
- Enter every priceUse the odds from one bookmaker for one market.
- Read the marginThe calculator adds up the implied chances and shows how far they go above 100%.
The formula
Book = 1 ÷ odds 1 + 1 ÷ odds 2 (+ 1 ÷ odds 3). Margin (overround) = book minus 100%. Payout rate = 100% ÷ book. Fair odds = odds × book.
Worked example: a 1X2 market
| Outcome | Odds | Implied chance | Fair chance | Fair odds |
|---|---|---|---|---|
| Home | 2.10 | 47.62% | 45.43% | 2.20 |
| Draw | 3.40 | 29.41% | 28.06% | 3.56 |
| Away | 3.60 | 27.78% | 26.50% | 3.77 |
The implied chances add up to 104.81%, a margin of 4.81%. Punters as a group get back about 95.41% of what they stake on this market.
Low-margin markets are not a gift, but they are a better starting point. Compare the same market at two or three bookmakers before you bet.
Margin calculator FAQ
What is a normal margin?
It varies by sport, league and market. Big football matches on main markets usually carry less margin than lower leagues, props or specials. Measure it rather than guess.
Why are fair odds higher than the bookmaker's?
Because the margin is removed. Fair odds are what a price would be if the bookmaker kept nothing.
Does the margin grow in an accumulator?
Yes, it compounds. Each leg passes on its own cut. Our margin guide shows the numbers.
Is the margin split evenly across outcomes?
Not always. We spread it in proportion to each price, the common method. Bookmakers often load more margin onto longer prices.