What is Margin?
Margin, in betting, is the share of total stakes a bookmaker expects to keep over time, derived from the overround built into its prices.
Margin and overround are related but not identical. A market with an overround of 104.7% has a theoretical margin of about 4.5%, calculated as 1 minus 1 divided by 1.047. On £1,000 of balanced stakes, the bookmaker would expect to retain about £45.
Actual results differ from theoretical margin because outcomes are unpredictable and money is rarely perfectly balanced. Operators report the actual percentage kept as the gross win margin or hold. Sportsbook hold can swing sharply from quarter to quarter depending on results, which often features in company earnings reports.
Higher margins on accumulators and same-game bet builders are one reason operators promote these products. Operators publish their actual sportsbook margin in results, and analysts compare it across companies and quarters.
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