An arbitrage, or "arb," exists when two books price opposite sides of the same market so generously that you can back both and profit no matter the result. It happens when the combined implied probability of the two best prices is under 100%. The arb margin is 1 - (1/decimalA + 1/decimalB): positive means risk-free profit, negative means betting both sides just locks in the hold.
Enter both prices and the total you want to stake. The calculator splits the stake so the payout is identical either way, and shows the guaranteed profit and return. Arbs move fast and books limit accounts that hammer them, so confirm both prices are still live before placing. To find arbs across every book automatically, use the Hedge Finder arb scan, and learn the mechanics on the Arbitrage Betting explainer.
The Odds Gap holds every book's price, so you do not have to type them in by hand. Skip straight to the live tools:
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