# Bookmaker margin calculator: how much does the bookie keep? > Free bookmaker margin calculator for UK bettors: enter fractional or decimal odds to see the overround, what the bookie keeps, the fair odds and which of two bookmakers pays more. - URL: https://safebet.ai/uk/sports-betting/margin-calculator/ - Markdown version: https://safebet.ai/uk/sports-betting/margin-calculator/index.html.md - Last updated: 2026-10-22 - Publisher: SafeBet.ai - Editorial policy and advertiser disclosure: https://safebet.ai/editorial-policy/ UK · Sports betting · Free tool Enter a bookmaker’s odds on every outcome of a market, in fractional or decimal format, to see how much it keeps, the fair odds with its margin removed, and, with a second bookmaker’s odds, which pays more on each outcome. By [SafeBet.ai Research Team](https://safebet.ai/editorial-policy/) Updated October 22, 2026 ## How the calculator works A bookmaker never offers fair odds. Add up the implied probabilities of every outcome in a market and you get more than 100%: the excess is the **overround**, and it’s how the bookie makes money whoever wins. At 10/11 on both sides of a two-way market, each side implies 52.4%, together 104.8%, and the bookmaker keeps about 4.5% of everything staked on that market over time. Enter the odds a bookmaker offers on each outcome, in fractional, decimal or American format, and the calculator shows how much it keeps, the share it pays back, and the fair odds with the margin removed. Add a second bookmaker’s odds on the same match to see which keeps less, and which pays more on each outcome. Comparing prices like this is the simplest way to cut what betting costs you, and betting exchanges, which charge commission on winnings instead, can be compared with our [exchange commission calculator](https://safebet.ai/uk/prediction-markets/commission-calculator/). ## Typical margins What a bookmaker keeps at common UK prices, computed with the same formula as the calculator. | Market and prices | Overround | Bookie keeps | Pays back | | ------------------------------------- | --------- | ------------ | --------- | | Two-way market at 10/11 and 10/11 | 4.76% | 4.55% | 95.45% | | Two-way market at 5/6 and 5/6 | 9.09% | 8.33% | 91.67% | | Two-way market at 4/5 and evens | 5.56% | 5.26% | 94.74% | | Football 1X2 at 11/10, 23/10 and 11/4 | 4.59% | 4.39% | 95.61% | | Football 1X2 at 5/4, 12/5 and 2/1 | 7.19% | 6.71% | 93.29% | [**Compare the 5 best sports betting sites in the UK** Ranked on regulation, fees, features and payouts · Sky Bet, bet365, Paddy Power and more See the ranking](https://safebet.ai/uk/sports-betting/) ## Frequently asked questions ### What is the overround? The amount by which a bookmaker’s implied probabilities add up to more than 100%. At 10/11 on both sides of a two-way market, each side implies 52.4%, together 104.8%, and the bookmaker keeps about 4.5% of everything staked on that market over time. ### How is what the bookie keeps calculated? Hold = 1 − 1 ÷ (sum of the implied probabilities), which is what the bookmaker keeps if bets follow the fair probabilities. The payout rate is the rest. The calculator removes the margin proportionally to get the fair odds. ### How do betting exchanges compare? Exchanges don’t build a margin into the odds: you bet against other users, and the exchange takes a commission on your net winnings. Use our [exchange commission calculator](https://safebet.ai/uk/prediction-markets/commission-calculator/) to compare an exchange price with a bookmaker’s. ### Does a lower margin mean I will win? No. It means you lose less on average. Even at a low margin, a bettor who picks at random loses part of everything staked over time. ## Keep reading [Methodology · 5 min **How we rank betting sites in the UK** We only rank bookmakers licensed by the Gambling Commission, at web addresses on its public register. Each is scored from 0 to 10 on six weighted criteria, licensing and safety, markets and features, odds and limits, payments and payouts, app and experience, and support and responsible gambling, and the ranking follows the overall scores. Fines and settlements lower the licensing score; we judge odds on what each bookmaker publishes, because their terms forbid automated odds collection; and we don't score bonuses. Read](https://safebet.ai/uk/sports-betting/how-we-rank/) [Guide · 2 min **Is sports betting legal in the UK? Licences, tax and the rules** Yes. Sports betting is legal in Great Britain with operators licensed by the Gambling Commission, for adults 18 and over, online and in betting shops. Bookmakers need a remote general betting licence and betting exchanges a betting intermediary licence; both are listed with their web addresses on the Commission's public register. Bettors pay no tax on winnings: the bookmaker pays General Betting Duty, and a new 25% rate for online bets applies from April 1, 2027. Read](https://safebet.ai/uk/sports-betting/is-sports-betting-legal/) Researched and written by [SafeBet.ai Research Team](https://safebet.ai/editorial-policy/) · Betting analysts & data scientists The team behind SafeBet.ai’s AI sports picks: data analysts, AI engineers and sports bettors based in Maastricht. Since 2021 our models have analyzed 30,088 matches. We review betting, casino and prediction-market platforms against a published methodology and cite official sources for every fact. [Editorial policy](https://safebet.ai/editorial-policy/) [How we rank](https://safebet.ai/uk/sports-betting/how-we-rank/) [About SafeBet.ai](https://safebet.ai/about/) [Report an error](https://safebet.ai/support/) 18+ Sports betting is legal in Great Britain only with operators licensed by the Gambling Commission, for adults 18+. Only play with money you can afford to lose. Gambling problem? Call [0808 8020 133](tel:+448088020133) (National Gambling Helpline, free and confidential, 24/7) or read our [responsible gambling guide](https://safebet.ai/uk/guides/gambling-help-uk/). Top 5 sports betting sites · UK 1. [1 **Sky Bet** Best overall 8.8](https://safebet.ai/uk/sports-betting/sky-bet-review/) 2. [2 **bet365** Biggest app & payout caps 8.6](https://safebet.ai/uk/sports-betting/bet365-review/) 3. [3 **Paddy Power** Best Odds Guaranteed 8.2](https://safebet.ai/uk/sports-betting/paddy-power-review/) 4. [4 **William Hill** 24/7 support 8.1](https://safebet.ai/uk/sports-betting/william-hill-review/) 5. [5 **Midnite** Esports betting 8.0](https://safebet.ai/uk/sports-betting/midnite-review/) [Full ranking](https://safebet.ai/uk/sports-betting/) Free sports betting site tools - [Sportsbook and exchange licence check (UK)](https://safebet.ai/uk/sports-betting/licence-check/) - [Bookmaker margin calculator (UK)](https://safebet.ai/uk/sports-betting/margin-calculator/) Sports betting guides - [Is sports betting legal?](https://safebet.ai/uk/sports-betting/is-sports-betting-legal/) - [How we rank sportsbooks](https://safebet.ai/uk/sports-betting/how-we-rank/)