| Outcome | Book | Odds | Share | Stake | Payout | Profit |
|---|---|---|---|---|---|---|
| Outcome 1 | FanDuel | +150 2.50 | $43.30 | $108.25 | +$8.25 | |
| Outcome 2 | DraftKings | −110 1.91 | $56.70 | $108.25 | +$8.25 |
Cents are rounded, so the payouts can differ by a penny or two once placed.
An arb is when different books disagree enough that you can back every outcome and still profit. Turn each price into an implied probability (1 ÷ decimal odds) and add them up. A fair market totals 100% and a normal one a bit more, which is the books' margin. Under 100% is an arb.
Each bet's share of the stake is its implied probability divided by the total, so every outcome pays back the same: the stake ÷ the market total. With +150 and −110, the market totals 40.0% + 52.4% = 92.4%, so $100 pays back $108.25 whatever happens.
Worth knowing
Edges are usually 1 to 3% and last minutes, so you need funded accounts at several books and a bankroll big enough for the return to matter. Odds comparison sites are the quickest way to spot them.
Using the arbitrage calculator
Check whether prices at different sportsbooks add up to a guaranteed profit, and split your stake so every outcome pays back the same.
- 1Enter the total you want to stake and pick the odds format.
- 2Enter the best price you can find for each outcome, from whichever book offers it.
- 3If the market totals under 100% it's an arb: place the bets shown, at the stakes shown, on each side.
Questions bettors ask
How do you know if it's an arbitrage bet?
Turn each outcome's odds into an implied probability (1 ÷ decimal odds) and add them up. Under 100% is an arb. +150 at one book and −110 at another total 40.0% + 52.4% = 92.4%, so it's an arb with about an 8% return.
How much do I bet on each side?
Each side's share of the stake is its implied probability divided by the total. In that example, $43.30 of $100 goes on +150 and $56.70 on −110, and either one pays back $108.25.
Is arbitrage betting legal?
Yes, it's just betting at more than one book. But sportsbooks don't like it and may limit the stakes on accounts that arb often, so many bettors spread their action and mix in regular bets.
What can go wrong?
Odds move, often within minutes, so a price can change before your second bet is placed. Bet the harder-to-get side first, check maximum stakes, and know each book's rules on voids and late changes, which can leave one side unhedged.