Definition
A sportsbook's margin (also overround or vig) and its payout percentage are two ways of expressing the same thing: how much of the money staked the book expects to keep. Margin is the amount by which the implied probabilities of all outcomes in a market sum above 100% - a two-way market priced so the implied probabilities total 105% has a 5% margin.
Payout percentage is the complement - roughly what proportion of stakes is returned to bettors as winnings over volume - so that 5% margin corresponds to about a 95% payout.
Margin varies a lot: by sport, by market (main match-result markets are usually keener than props or long accumulators), by operator, and by whether the event is high-profile. Lower margin on a market genuinely means better value for the bettor there, and it is one of the few objective, comparable measures of how competitive an operator's pricing is.
In context
For affiliates, margin comparison is one of the most genuinely useful, objective things a sportsbook review can provide, and it is under-covered because it takes work. Content that calculates and shows the margin on comparable markets (for example the main match-result market of a top football league) across several operators gives readers a real basis for choosing where to bet, in contrast to reviews that rank on bonus size.
It can also explain that a bettor should line-shop - check the same selection across licensed books - because the differences in price are money.
Honest framing matters. A lower margin is better value but does not make betting profitable - the margin still favours the book, and it compounds across the legs of an accumulator, which is why long accas have a much worse effective payout than singles.
Content should show margins by market type so readers understand that props, specials and multi-leg bets carry higher margins than main markets. It should present margin as a value comparison tool, not as a route to winning, and carry standard age-gating and responsible-gambling messaging.
Ranking operators partly on the margin of their core markets is a defensible, reader-serving methodology.
Worked example
An affiliate's sportsbook comparison calculates the margin on the same top-league match-result market across five operators (ranging from about 3% to 7%) and on a player-props market (all above 10%), showing readers which book offers better value on core markets. It explains lower margin is better value but the book still holds an edge, and carries age and responsible-gambling messaging.
Related terms
Frequently asked questions
Browse more iGaming terms in our glossary.
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