Arbitrage (Sure Bet) Calculator
Free · No signup · Works in your browser
Enter the two decimal odds for the opposite outcomes of an event (ideally the best price for each from different bookmakers) and your total stake. The calculator tells you whether it's an arbitrage, the guaranteed profit, and exactly how much to stake on each side.
Enter your odds and stake to check for an arb.
How the arb check works
Every decimal price is a probability in disguise: implied probability = 1 ÷ odds. Add the two implied probabilities. If the total is below 100%, the two books disagree enough that you can back both sides for a guaranteed profit:
Arb % = (1 ÷ combined implied probability − 1) × 100.
Split the stake in proportion to each side's implied probability so both return the same. Example: 2.05 and 2.10 give 1/2.05 + 1/2.10 = 0.488 + 0.476 = 0.964 (96.4%) — a ~3.7% arb. On $100 you'd stake ~$50.60 and ~$49.40, and get back ~$103.70 either way.
The honest catch
The maths is real, but making money from arbs is not easy: they're usually small (1–3%), they vanish as odds move before you place both legs, and bookmakers quickly limit or close accounts they suspect of arbing. Read the full picture in our arbitrage betting guide. To read any price as a probability, use the Odds Converter, and to measure a single book's margin use the Margin Calculator.
Calculations are exact from the numbers you enter. This tool assumes both bets pay out on the stated decimal odds and ignores commissions, exchange fees and bet limits.
Related guides & tools
- Arbitrage betting (sure bets) explained — the full method and the honest catch.
- The bookmaker margin (vig) — why one book's prices add up to over 100%.
- Margin & Fair Odds Calculator — measure a single market's built-in edge.
- Odds Converter — turn any price into its implied probability.