About this tool
The Arbitrage (Sure Bet) Calculator checks whether the best available prices across different books let you back every outcome and still guarantee a profit. For each outcome it takes the decimal odds and forms the arbitrage sum, Σ(1/d_i). When that sum is below 1 an arbitrage exists: the market's combined implied probability is under 100%, so a correctly split stake returns the same amount whichever result comes in. The guaranteed ROI is (1/arb-sum − 1) × 100.
Every figure is computed locally in your browser and nothing you enter is uploaded. Enter a total budget and the best odds for two outcomes (a moneyline) or add a third for a 3-way market such as football's home/draw/away. Odds can be American, decimal, or fractional — the tool converts them and then allocates stake_i = T × (1/d_i) / arb-sum to each outcome, which equalises the return at T / arb-sum. The difference between that return and your budget is the locked profit.
This is a pure math reference and does not place bets or handle real money. Real arbitrages are small and fleeting: prices move, limits and rules apply, and books may void bets, so treat the output as the theoretical split at the exact odds you entered. Always round stakes to what each book allows and re-check the prices before committing.