An arbitrage (or "sure bet") exists when the implied probabilities of every outcome across different sportsbooks add up to less than 100%. Enter up to 4 outcomes in American odds plus your total stake — we'll tell you if an arb exists and exactly how much to bet on each side. Last updated: May 2026.
| # | American Odds | Implied % | Stake | Payout |
|---|---|---|---|---|
| 1 | — | — | — | |
| 2 | — | — | — | |
| 3 | — | — | — | |
| 4 | — | — | — |
The engine behind a sure bet is a single test: convert every outcome's American odds to decimal, then add up the implied probabilities, where each outcome's implied probability is 1 ÷ decimal odds. If that sum — what the calculator labels "Arb %" — comes out below 1.0 (100%), an arbitrage exists, because the combined market is pricing the event at less than a certain 100%. The further below 100% the sum lands, the larger your guaranteed edge.
When an arb is present, the tool splits your stake so every outcome returns the same amount. For each side it computes stake = (total ÷ decimal odds) ÷ arb-sum, and your locked-in return is total ÷ arb-sum regardless of which result hits. Guaranteed profit is that return minus your total stake, and ROI is profit divided by stake. Because the payouts are equalized, the result is the same money in your pocket no matter how the game ends.
Use the defaults: outcome 1 at +150, outcome 2 at −130, with a $100 total stake. Convert each: +150 → (150 ÷ 100) + 1 = 2.50 decimal, implied 1 ÷ 2.50 = 40.00%. −130 → (100 ÷ 130) + 1 = 1.769 decimal, implied 1 ÷ 1.769 = 56.52%. The arb sum is 40.00% + 56.52% = 96.52% — under 100%, so a sure bet exists.
Your guaranteed return is $100 ÷ 0.9652 = $103.60, a guaranteed profit of $3.60 and ROI of 3.60%. The stake split: side 1 = ($100 ÷ 2.50) ÷ 0.9652 = $41.44; side 2 = ($100 ÷ 1.769) ÷ 0.9652 = $58.56. Check it: $41.44 × 2.50 = $103.60, and $58.56 × 1.769 = $103.60. Whichever outcome wins, you collect the same $103.60 — that's the arbitrage.
I treat the calculator's profit figure as a best case. Between line moves, limits, and the odd voided wager, the realized edge on small arbs is often razor-thin — never bet money you can't afford to have stuck on one side.
Arbitrage is placing bets on every possible outcome of an event across different sportsbooks at prices that guarantee a profit regardless of which outcome wins. It exists because books disagree.
Convert every outcome's American odds to decimal, then sum 1 ÷ decimal_odds for all outcomes. If the total is less than 1.0 (100%), an arb exists. The smaller the sum, the bigger the guaranteed edge.
For each outcome, stake = (total_stake ÷ decimal_odds) ÷ arb_sum. This equalizes the payout no matter which outcome hits, leaving a fixed guaranteed return.
Yes, in jurisdictions where sports betting itself is legal. However, sportsbooks routinely limit or close accounts of bettors they detect using arbitrage strategies.
Books adjust lines constantly. Most arbs disappear within minutes as books rebalance their books or copy each other's prices. You need to act quickly and accept that some opportunities will close before you place all your bets.