Overround vs Bookmaker Margin
What each means, how they relate, and when to use which.These are two expressions of the same edge. Overround is the sum of a market's implied probabilities exceeding 100%; bookmaker margin restates that overshoot as the percentage advantage the book holds. If a market's implied probabilities total 105%, the overround is 5 points and the margin is close to it.
The bookmaker's built-in margin, visible when the odds across all outcomes of a market imply probabilities that add up to more than 100%.
Use it when Use overround for the raw sum of implied probabilities over 100%.
Full definition of Overround →The bookmaker's built-in edge, seen when the implied probabilities of all outcomes in a market sum to more than 100%.
Use it when Use bookmaker margin for the tidy percentage edge you compare across books.
Full definition of Bookmaker Margin →The key distinction
- Overround is stated as total implied probability above 100%; margin is stated as an edge percentage.
- They are derived from the same odds and move together.
- Overround is the raw signal; margin is the normalised comparison figure.
Common questions
What's the difference between Overround and Bookmaker Margin?
These are two expressions of the same edge. Overround is the sum of a market's implied probabilities exceeding 100%; bookmaker margin restates that overshoot as the percentage advantage the book holds. If a market's implied probabilities total 105%, the overround is 5 points and the margin is close to it.
What is Overround?
The bookmaker's built-in margin, visible when the odds across all outcomes of a market imply probabilities that add up to more than 100%.
What is Bookmaker Margin?
The bookmaker's built-in edge, seen when the implied probabilities of all outcomes in a market sum to more than 100%.
More term comparisons
Understanding, not advice. This explains how two terms differ so you can read the industry clearly. Nothing here treats gambling as a way to make money; the maths favours the house. 18+.