Arbitrage Calculator
Drop in prices from two bookmakers for the same event, and this checks whether a real arbitrage exists between them — and exactly how to split your stake if it does.
Key terms, plainly put
An arbitrage turns up when two bookmakers disagree enough on the same event that backing both outcomes, split correctly, locks in a profit no matter the result. It only exists because prices differ — the moment both firms agree closely, the gap closes.
The maths behind it
Market total = (1 ÷ price A) + (1 ÷ price B). Below 100%, an arbitrage exists. Split your total stake in proportion to each side's share of that sum, and whichever outcome happens, the payout comes out the same.
Worked example
Price A at 2.10, price B at 2.05: (1÷2.10) + (1÷2.05) = 0.476 + 0.488 = 0.964, or 96.4% — under 100%, so there's a genuine arbitrage. Splitting £100 correctly locks in roughly £103.80 back whichever side wins, about £3.80 guaranteed profit.
Common questions
If the maths guarantees profit, why isn't everyone doing it?
A few things get in the way in practice: prices can move before your second bet lands, bookmakers restrict accounts that do this often, and thin margins can vanish once fees or stake limits are counted.
What counts as a decent arbitrage percentage?
Anything under 100% technically qualifies. The lower it goes, the bigger the guaranteed margin — but wide gaps are rare and tend to close fast once spotted.