Overround calculator (bookmaker margin)
The overround is how far a bookmaker’s implied probabilities add up above 100%: Σ(1/odds) − 1. It is the bookmaker’s built-in margin — the lower it is, the better the prices you get.
Updated 19 October 2026 · Free, no sign-up. All calculations run in your browser. 18+ · Play responsibly.
How it works
- Enter one bookmaker’s odds for every outcome of the same market.
- The calculator adds the implied probabilities: anything above 100% is the overround.
- It also shows the payout and the fair odds with the margin removed.
The formula
Overround = Σ(1/odds) − 1 · Payout = 1 ÷ Σ(1/odds) · Margin (hold) = 1 − payout
Overround and margin are close but not equal: an overround of 3.89% means the bookmaker keeps 3.75% of what is staked when the money is spread in proportion to the prices.
Worked example
A 1X2 market at 2.50 / 3.40 / 2.90: 0.400 + 0.294 + 0.345 = 1.039. The overround is 3.89%, the payout 96.25% and the margin 3.75%. Fair odds without the margin: 2.60 / 3.53 / 3.01.
Why it matters
The same bet at a 2% margin and at an 8% margin can differ by several percent in price. Comparing overrounds shows which bookmaker gives the most back — and the lowest-margin prices are the best starting point for fair odds.
FAQ
What is a normal overround in football?
Sharp bookmakers often run about 2–3% on major 1X2 markets; many recreational bookmakers run 5–8% or more, higher on smaller leagues and long shots.
Overround or margin — which one do bookmakers quote?
Both are used. Overround is the simple sum minus 100%; margin (hold) is the share of stakes the bookmaker keeps. This calculator shows both.