Free arbitrage (sure bet) calculator. Split your stake across two outcomes to lock in guaranteed profit, with the arb percentage shown.
Arbitrage betting (also called "arbing" or a "sure bet") means backing every outcome of an event across different bookmakers whose odds are high enough that, together, they guarantee a profit no matter the result. It exists when bookmakers disagree on the odds. This calculator splits your total stake so the return is identical whichever outcome wins.
Two bookmakers both price the two outcomes at 2.10. Arb value = (1/2.10 + 1/2.10) × 100 = 95.24%, which is under 100%, so an arb exists. Splitting $100 gives $50 on each; whichever wins, you get $105 back — a guaranteed $5 (5%) profit.
Arbs are usually small and short-lived, odds move fast, and bookmakers may void bets or limit accounts. Always double-check the odds are still live before placing both sides.