Free tool
Arbitrage Calculator
Two books, opposite sides, prices that don't agree. Enter both odds and your total stake — we'll split the wager so you profit no matter who wins.
Best price you can get on A
Best price you can get on B
$
Combined risk across both books
Arbitrage opportunity
+$49.40
+4.94% ROI · +4.71% arb margin
Bet on Side A
$488.10
Returns $1049.40 if A wins
Bet on Side B
$511.90
Returns $1049.40 if B wins
How arbitrage actually works in practice
An arb exists when the implied probabilities of opposite sides — at two different books — sum to less than 100%. That gap is your guaranteed profit margin.
arb_pct = 1 − (1/decimalA + 1/decimalB)
stake_A = total × (1/decimalA) / inv_sum
stake_A = total × (1/decimalA) / inv_sum
Real-world frictions you should plan around:
- Limits. Sharp opportunities get small fast. Books can void or limit your stake before the second leg confirms.
- Account flagging. Most US books detect arb activity and limit/close accounts after a handful of confirmed arbs.
- Line movement. If one leg moves between you placing the first and second bet, your arb can disappear or invert.
- Bonus / promo arbs (using free bets and odds boosts) are usually safer and more sustainable than pure-line arbs.
The realistic edge: 0.5-2% margins are typical when they exist; 3%+ is rare and usually comes from a stale line or promo.