Arbitrage Betting Calculator

Enter your total stake and the odds for each outcome to check whether the combined book percentage is below 100%. Decimal (2.10), fractional (11/10) and American (+110 or -120) odds all work. Add a commission percentage on any leg placed at a betting exchange.

Total stake Outcome 1 odds Outcome 1 commission %, optional Outcome 2 odds Outcome 2 commission %, optional Outcome 3 odds, optional Outcome 3 commission %, optional

Formula

Book percentage = 1/odds A + 1/odds B + optional 1/odds C. If the percentage is below 100%, the difference is the theoretical arbitrage margin before errors, voids, limits, fees and odds movement.

Fractional odds convert as a/b + 1, so 11/10 becomes 2.10. American odds convert as odds/100 + 1 when positive and 100/|odds| + 1 when negative, so +110 becomes 2.10 and -120 becomes 1.83.

Exchange commission is charged on net winnings, not on the full return, so it only reduces the profit portion of the price: odds of 3.00 at 5% commission pay 1 + 2.00 × 0.95 = 2.90. The calculator applies that adjustment before splitting stakes, which is why an arb that looks profitable at raw exchange odds often is not.