Arbitrage calculator
Enter a price on each side of a market from two different places. This says whether the pair leaves a gap, how to split your money across them, and what the return comes to.
Arbitrage calculator
When two books disagree enough, you can back both sides and win either way. Put the best price on each side in, plus what you want to put at risk in total, and this splits it.
Prices move while you are placing the second leg, and books limit or void accounts that do this often. Treat the number as the best case, not the expected case.
When two prices disagree
An arbitrage exists when the implied chances on the two sides of a market, taken from two different places, add up to less than 100%. Normally they add up to more, because both books have charged their margin. When they add up to less, the two prices disagree by more than the combined margin and a stake split correctly across them returns the same amount whichever way the game goes.
The split is not even. The money has to be divided in proportion to the prices, so the shorter side takes more of it. Getting that split wrong is the usual way a genuine arbitrage turns into an accidental bet on one outcome.
Gaps like this are usually small and usually brief. They appear when one book moves a line and another has not yet, and they are most common between a traditional sportsbook and an exchange, because the two price things in completely different ways.
The practical obstacles are not in the maths. The price can move while you are placing the second leg, a book can void a bet after the fact, maximum stakes can be lower than the arbitrage needs, and accounts that only ever appear for this get their limits cut. Those are real costs and they belong in the decision.
Questions people ask about this one
How is this different from a hedge?
A hedge starts from a bet you already hold and covers it. An arbitrage is both legs placed deliberately, at the same time, because the pair of prices is mispriced against each other.
Are sportsbooks allowed to limit me for this?
Yes, and they do. It is the standard response, it is in the terms, and it usually arrives as quietly reduced maximum stakes rather than a closed account. It is the real long term cost of the strategy.
Why do I so rarely see a gap?
Because they close fast and because the margin has to be beaten on both sides at once. Promotions are the reliable version of the same idea: the edge is handed to you by the sportsbook rather than found in a pricing error.
The other calculators
Expected value, parlay odds, Kelly staking, prediction market prices and the bonus bet converter are all on the main calculators page, free and with no account. How these numbers feed the rest of the product is set out in the methodology.