Bookmaker Margin, Payback & Arbitrage Calculator
Understand the price. Check the numbers.
Free to use · No sign-in needed · Calculations stay in your browserMarket margin & arbitrage
Check a bookmaker’s theoretical payback, or combine the best prices across bookmakers to check for arbitrage.
Your selections
Manual oddsIllustrative prices to start. Each tab keeps its own inputs. Use a complete market with matching settlement rules.
Decimal odds include your stake. Example: 2.50.
Your calculation
Updates instantlyA price-based market measure, not your expected ROI or the bookmaker’s realised payout.
- Overround
- 4.71%Implied total minus 100%
- Implied total
- 104.71%Sum of 1 ÷ each decimal price
Equal-return staking cannot create a profit across every outcome at these prices.
| Selection | Stake | Return | Profit |
|---|---|---|---|
| Selection A50.00% of stake | €250.00 | €477.50 | -€22.50 |
| Selection B50.00% of stake | €250.00 | €477.50 | -€22.50 |
Each return assumes only that row wins; profit subtracts the entire budget. Stakes sum exactly to your total. Returns use cent rounding; bookmaker rounding may differ.
Payback and arbitrage use the same maths
Add 1 ÷ odds for every outcome. Payback = 100 ÷ that sum. Overround = (sum − 1) × 100. At 1.91 / 1.91, payback is 95.50% and overround is 4.71%—these are not complements.
Stake per selection = total stake × (1 ÷ its decimal odds) ÷ the sum of inverse odds.
Include every possible outcome: football 1X2 needs home, draw and away. Use one bookmaker’s complete market to measure its payback, or the best matching prices across books to check arbitrage.
These calculations assume one full winner and full losses on the other selections. Pushes, dead heats, half wins/losses, exchange commission, taxes, fees, free bets and settlement differences are not modelled. Prices, available stakes and bookmaker limits can change before bets are accepted.
Calculation tools, not betting recommendations. Nothing is added to your ledger and no bets are placed. Currency changes the display only, not exchange rates. Gambling involves risk—only stake what you can afford to lose.