Sportsbook

Bookmaker margin: the edge built into the odds

Bookmaker margin (overround) is the edge built into the odds: how far the implied probabilities of all outcomes in a market add up above 100%. On a 1.90 / 1.90 market the total is 105.3%, a margin of about 5.3%. Margin is the price, while hold shows what was actually kept.

Yevhen SychovOctober 2026

Formula and example

Margin = sum of the probabilities of all outcomes minus 100%The probability of an outcome in the price = 1 / odds. A 1.90 / 1.90 market: 52.6% per outcome, 105.3% in total, a margin of about 5.3%.

Without a margin, both sides would be priced at 2.00. With balanced betting, the bookmaker keeps 5% of turnover: out of €200 in bets, €100 on each side, it pays out €190. A 5.3% margin and a 5% share of turnover are close but different numbers.

What drives it

Lower marginHigher margin
Eventpopular sports and top leaguesniche sports and lower leagues
Timingpre-matchin-play
Marketmain outcomes, handicaps and totalscorrect score, specials, outrights

On popular events players compare prices, and a high margin drives them to competitors. On niche markets the line is less accurate, and the margin protects against pricing errors. In-play prices change fast, so the buffer there is bigger too.

Margin vs hold

Margin is the theory built into the price in advance. Hold is the fact: GGR divided by total stakes for the period. Over the long run hold tends towards the average margin across all markets and bet types, while over the short run match results move it.

Accumulators push hold above the margin on singles: their margin grows with every selection. Hold that stays below margin is a sign that the line is being beaten, for example by professional players.

Common mistakes

  • Comparing margin with hold over a week. One match with almost all bets on one side shifts hold more than any line settings.
  • A low margin on a weak line. Professionals are the first to find a niche market with a margin like a top match.
  • Not counting a margin cut as a promo. A better-than-market price on a popular event is a cost, like boosted odds, and its effect is measured against a control group.
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