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MGBetting · 8 min read

Sportsbook margin, explained

How overround is computed, and why one market is not enough

CSCryptoSlotGuide editorial desk
The short version
Margin is the overround baked into the price
Compare across many markets, not one
One point of margin beats any welcome offer

Margin, or overround, is the amount by which a book's implied probabilities exceed 100%. It is the sportsbook equivalent of RTP, and unlike a bonus it applies to every bet you place.

To compare books fairly, take the same markets across football, basketball, tennis and esports, at the same time of day, and look at the median rather than one price. Books quote tighter on marquee events and wider on everything else, so a single-market comparison is misleading.

A book a point tighter costs you less over a season than any promotion returns. It is the least visible and most important number on a sportsbook.

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