In short: Sportsbooks make money by pricing a margin into their odds, so the implied chances of all outcomes add up to more than 100%. If stakes are spread across outcomes, the book keeps the difference whatever happens. What it actually keeps, its hold, depends on how balanced the bets are, the bet mix and how well it manages risk.
Last reviewed: 30 October 2026.
A sportsbook is not betting against its players in the way a player bets against the book. It is pricing a market, collecting stakes and paying winners, and its income comes from the gap between what it takes in and what it pays out. This guide explains where that gap comes from: overround, margin, hold and the bet types that change them, with worked examples you can check yourself. If you are new to the model, start with what a sportsbook is.
The short answer: the margin is in the price
Every price a sportsbook offers carries a chance. In decimal odds, the implied probability is 1 divided by the odds: a price of 2.00 implies 50%, a price of 1.50 implies 66.7%. In a fair market with no margin, the implied probabilities of all outcomes add up to exactly 100%.
A sportsbook shortens every price a little, so the total comes to more than 100%. That excess is the overround. It means the book pays winners slightly less than fair odds would, and across many bets that difference becomes revenue.
Overround and margin, with worked examples
Take an illustrative tennis match where both players are priced at 1.90.
| Outcome | Decimal odds | Implied probability (1 / odds) |
|---|---|---|
| Player A | 1.90 | 52.63% |
| Player B | 1.90 | 52.63% |
| Total (book) | 105.26% |
The overround is 5.26%. The margin, the share of all stakes the book keeps when money is spread in line with its prices, is calculated as 1 minus 1 divided by the book total: 1 − 1/1.0526 = 5.0%. The two numbers are close but not the same, and they are often mixed up. Overround describes the prices; margin describes the expected share of stakes the book keeps.
Check it with money. If players stake $1,000 on each player, the book takes $2,000. Whoever wins, it pays $1,000 × 1.90 = $1,900, and keeps $100, which is 5.0% of the $2,000 staked.
A three-way football market works the same way. Illustrative prices of 2.10 home, 3.40 draw and 3.60 away imply 47.62% + 29.41% + 27.78% = 104.81%. The margin is 1 − 1/1.0481 = 4.6%.
Operators set margins per sport, competition, market and time before the event. A popular match-winner market and a niche player prop can carry very different margins, and the same market can be repriced many times as information and money arrive.
Hold: what the sportsbook actually keeps
Margin is the theory. Hold is the result: the stakes a sportsbook took minus the winnings it paid, as a share of the stakes.
Hold = (total stakes − total winnings paid) ÷ total stakes
Hold only matches the margin when money is spread in line with the prices. Real books are rarely like that. Take the same tennis match at 1.90 each, but with $1,000 staked on Player A and $600 on Player B, $1,600 in total:
| Result | Paid to winners | Book result | Hold |
|---|---|---|---|
| Player A wins | $1,000 × 1.90 = $1,900 | −$300 | −18.75% |
| Player B wins | $600 × 1.90 = $1,140 | +$460 | +28.75% |
On one event, the result swings far from the 5% margin either way. Over thousands of events, a sportsbook with sound prices expects the swings to even out towards its margin, but a run of popular favourites winning can still hurt a week or a month. That is why sportsbooks manage liability, not only prices.
How sportsbooks manage risk
- Moving the odds. When too much money lands on one side, the book shortens that price and lengthens the other to attract balancing bets.
- Stake limits. Maximum stakes per market, per event and per player cap how much any single result can cost.
- Profiling accounts. Risk teams watch for players who consistently beat the closing price and adjust their limits.
- Suspending markets. In live betting, markets are suspended during moments such as a goal or a penalty, so no one bets on information the price does not yet reflect.
- Trading the feed. Most operators take prices and results from an odds feed and trading service, then set their own margins and limits on top.
Why parlays and accumulators earn the book more
An accumulator (parlay) combines several selections into one bet, and the odds are multiplied. So is the margin. With a 5% margin on each leg, the player gets about 95% of fair value per leg:
| Legs | Share of fair value returned (0.95 per leg) | Effective margin |
|---|---|---|
| 1 | 95.0% | 5.0% |
| 2 | 90.3% | 9.8% |
| 3 | 85.7% | 14.3% |
| 4 | 81.5% | 18.5% |
This is why accumulators, bet builders and same-game combinations matter so much to sportsbook revenue: each extra leg compounds the margin. It is also why a sportsbook’s hold depends on its bet mix as much as on its prices. Two books with identical margins can report different holds if one takes far more multiples than the other.
Other income and the costs against it
Beyond the margin on single and multiple bets, sportsbooks earn from features such as cash-out, where the offered settlement value usually carries its own margin, and from cross-selling players into a casino on the same account.
Against that income sit the costs of running the book: the odds feed and trading service, payment processing, licence and compliance, taxes or duties where they apply, bonuses and free bets, affiliate or agent commission, and marketing. The margin pays for all of it.
How it shows up in GGR and NGR
Hold is a percentage; gross gaming revenue (GGR) is the amount: total stakes minus winnings paid. In the tennis example where Player B won, GGR was $460. Net gaming revenue (NGR) then subtracts items such as bonuses and free bets, and, depending on the contract or the regulator, taxes and some fees. Platform and partner fees are often calculated on one of the two, so the definition in your contract matters. We explain the formulas and include a calculator in GGR vs NGR.
Running a sportsbook on Spinlab
On Spinlab, sportsbook integration comes with the Dominate plan, with a FeedConstruct feed, on the same back office as the casino, so players use one account and one wallet. Dominate is $2,499/mo billed annually on spinlab.studio/pricing at the time of writing (30 October 2026). Sportsbook fees, margins and risk settings for your markets are discussed on the demo call. See our sportsbook software page for what is included, and the step-by-step guide on how to start a sportsbook.
Frequently Asked Questions
Do sportsbooks want you to lose?
Not on any single bet. A sportsbook earns from the margin across all bets, so it wants balanced money and fair prices. Individual winners are part of the model; what hurts a book is heavy one-sided liability or prices that are wrong.
What is the difference between overround and margin?
Overround is how far the implied probabilities exceed 100% (5.26% in a 1.90/1.90 market). Margin is the share of stakes the book expects to keep from that market (5.0% in the same example), calculated as 1 minus 1 divided by the book total.
What is hold in sports betting?
Hold is what the sportsbook kept, stakes minus winnings paid, divided by stakes. It is the actual result over a period, while margin is the expected result built into the prices.
Can a sportsbook lose money?
Yes. On a single event or a short period, one-sided betting can produce a loss, as in the example where Player A wins. Over a large number of bets, sound pricing and risk management should bring the result back towards the margin.
Why do sportsbooks promote accumulators?
Because the margin compounds with every leg. A four-leg accumulator with a 5% margin per leg carries an effective margin of about 18.5%, while paying the player large headline odds.
How do I calculate the margin in a market?
Add up 1 divided by each decimal price to get the book total, then calculate 1 minus 1 divided by that total. Prices of 2.10, 3.40 and 3.60 give a book total of 1.0481 and a margin of about 4.6%.
Next step
If you are planning a sportsbook or adding one to a casino, book a demo and we will walk through the sportsbook, feed and risk settings in the back office, or read what our sportsbook software includes first.
