Sports betting arbitrage is betting both sides of the same market at two sportsbooks whose prices disagree enough that the pair pays out either way: whichever side wins, you get back more than your total stake. It's possible when the two prices' implied probabilities add up to less than 100%. The margin is usually small, and it holds only if both bets stand at the prices you took.
How it works
Every price implies a probability. One book prices both sides of a market so they add up to more than 100%, and the extra is its margin. Two books don't always agree, though. When the best price on each side comes from a different book, the pair can add up to less than 100%. That shortfall is the arb.
To check a pair, convert both prices to decimal odds (d):
- Plus prices:
d = 1 + odds / 100 - Minus prices:
d = 1 + 100 / |odds|
Then add the implied probabilities. The pair is an arb when:
1/d1 + 1/d2 < 1
Split your total stake in proportion to those implied probabilities, and both outcomes pay the same:
stake on side 1 = total × (1/d1) ÷ (1/d1 + 1/d2)profit % = 1 ÷ (1/d1 + 1/d2) - 1
A worked example
These prices are hypothetical. Book A has Over 47.5 at +120, and Book B has Under 47.5 at -115.
| Side | Price | Decimal | 1/d |
|---|---|---|---|
| Over 47.5 at Book A | +120 | 2.2000 | 0.4545 |
| Under 47.5 at Book B | -115 | 1.8696 | 0.5349 |
| Total | 0.9894 |
0.9894 is under 1, so the pair is an arb: together the two sides imply 98.94%. The profit is 1 ÷ 0.9894 - 1, about 1.07% of the total stake.
Split a $100 total:
- Over:
100 × 0.4545 ÷ 0.9894= $45.94 - Under:
100 × 0.5349 ÷ 0.9894= $54.06
Then the payout is the same either way:
| Result | Winning bet returns | Net on $100 staked |
|---|---|---|
| Over wins | $45.94 × 2.20 = $101.07 | +$1.07 |
| Under wins | $54.06 × 1.8696 = $101.07 | +$1.07 |
The losing bet is already counted: you staked $100 across both books, and $101.07 comes back.
Now suppose the Under moves to -125 before you place it. Its 1/d becomes 0.5556, the pair adds up to 1.0101, and no stake split pays out either way. That's why the order and speed of the two bets matter.
How to find arbitrage bets
By hand:
- Pick a market at least two of your books offer, and match it exactly: same game, side, line and period.
- Find the best price on each side across the books you can bet at.
- Convert both prices to decimal and add
1/d1 + 1/d2. Under 1 is an arb. At 1 or above, it isn't. - Split the stake with the formula above, or enter both prices in the free arbitrage calculator.
- Read both books' rules for that market: overtime, voids and pushes.
- Bet the side more likely to move first, then the other. Check that both tickets show the prices you planned on.
Steps 1 to 3 are the slow part. Checking every market across several books by hand takes a long time, and arbs often close within seconds as books adjust their lines.
The Arbitrage scanner on Unjuiced runs that check for you, pregame and live, across the books you choose. Each row shows both sides with their books and prices, and the Profit % on your total stake. A 1 beside a side means bet that one first, because its price is the most likely to move. Press a row and the calculator splits your total stake. Open both then opens the two books at once. Unjuiced doesn't place bets, so you still confirm each price at the book. The Arbitrage tool guide walks through a row, and the Arbitrage feature page covers the filters.
Risks
An arb takes the result of the game out of the question. It doesn't take out these:
- The price moves before your second bet. Then the pair may no longer pay out either way, and you hold an open bet until you cover it. The example above stops being an arb when the Under goes from -115 to -125. See what to do if a price moves.
- A leg is voided or settles differently. Rules differ by book. One book's total may include overtime and the other's may not. A player prop may be voided at one book and graded at the other if the player doesn't play. A book can also cancel a bet it says was posted at an obvious error. Whole-number lines can push.
- Stake limits. A book may accept less than you asked for. Your stakes then no longer balance, and one outcome pays less.
- Accounts getting limited. Books can lower the maximum stake on, or close, accounts that bet arbs often.
- Rounding and fees. Rounding a stake changes that side's payout. A prediction market's fees change what its leg really pays.
- Money tied up. Both stakes sit at their books until the game settles.
Questions
Is sports betting arbitrage legal?
Generally, yes, where sports betting itself is legal: an arb is two ordinary bets placed at two books. Books can still limit or close accounts that bet arbs, and their terms differ, so check each book's terms and your local law before you bet.
Can an arbitrage bet lose money?
Yes. A pair pays out either way only if both bets stand at the prices you took. A price can move before the second bet, a book can void or settle one leg differently, and a stake limit can leave one side short.
How much does an arb pay?
Usually a small share of the total stake. In the example on this page, $100 split across +120 and -115 returns $101.07 whichever side wins, a 1.07% profit before any rounding or fees.
Why do sportsbooks limit arbitrage bettors?
An arb usually means one book's price is out of line with the rest of the market. A book that sees an account mostly taking those prices can lower its maximum stake or close it.
What is the difference between arbitrage and a middle?
An arb bets both sides of the same line so that either result pays out. A middle bets an Over at a low line and an Under at a higher line at different books: both bets win if the result lands between the lines, and it usually loses a little if it doesn't.