Measure Any Market’s Overround
Why Margin Is the Number That Matters
Add up the implied probabilities (100 ÷ decimal odds) of every outcome in a market. A fair book sums to 100%; everything above that is the bookmaker’s built-in edge. A typical football 1X2 runs 4–7%; racing markets often run far higher. Margin is the real price of betting — and it compounds over every bet you place.
Frequently Asked Questions
What is a bookmaker margin or overround?
The amount by which the implied probabilities of all outcomes exceed 100%. It is the bookmaker's built-in edge on the market.
What is a good betting margin?
5% or under on football 1X2 is competitive. Above 8%, you are paying heavily for every bet.
How do I calculate implied probability?
100 divided by the decimal odds: odds of 2.0 imply 50%.