Key takeaways

• Arbitrage betting means backing every outcome of an event at different books, with stakes sized so every outcome pays the same amount.

• It works when the best prices across books add up to less than 100% implied probability.

• On $1,000 at +105 at one book and +102 at another, the right split locks in $17.44 whichever side wins.

• Arbers lose money on execution, usually a leg that misses its price or a fee that's bigger than the margin.

Arbitrage betting in one paragraph

Sportsbooks and prediction markets price the same game independently, and their prices don't always agree. When one book's price on Team A and another's price on Team B are both generous enough, betting both sides in the right proportions returns more than the total staked, no matter who wins. That's an arb, short for arbitrage. The profit is a small share of the stake, and it's locked in the moment both bets are placed.

A worked example

Say FanDuel has Side A at +105 and a prediction market such as Novig has Side B at +102.

• +105 implies 48.78% and +102 implies 49.50%. Together they come to 98.29%, under 100%.

• On $1,000, the stakes are $496.31 on Side A and $503.69 on Side B.

• Either side returns $1,017.44, so the profit is $17.44.

Run any pair of prices through the arbitrage calculator to see the split and the profit.

Where the risk sits

Execution is where an arb can go wrong:

• A price can move before the second bet goes in, leaving a normal bet on one side.

• A fee on a prediction market leg can be bigger than the arb itself.

• Sportsbooks limit accounts that keep taking off-market prices.

• Two legs can settle differently if their rules on overtime or postponements don't match.

Each of these has its own guide below.

Guides on this site

• How to find arbitrage bets: a manual price-comparison workflow and when a scanner pays for itself.

• Arbitrage betting math: implied probability, the 100% test and worked two-way and three-way examples.

• Stake sizing and rounding: how to split, round and cap each leg, and what fees do to the split.

• Arbitrage with no-vig prediction markets: using Novig, Kalshi, Polymarket US or ProphetX as one leg.

• Sportsbook account limits: why FanDuel, DraftKings and other books limit arbers, and what Massachusetts found.

• Common arbitrage mistakes: the errors that turn a locked profit into a loss.

• Is arbitrage betting legal?: the short answer, sportsbook terms and where prediction markets fit.

Arbitrage betting basics questions

Is arbitrage betting risk-free?

The outcome risk is gone once both legs are placed at the checked prices. The execution risks above remain, which is why arbers check prices, fees and rules before the first bet.

How much can you make?

The return depends on the prices. The examples on this site return between 1.11% and 2.02% of the total stake before fees.

Do I need software?

No. The calculator covers the math. Scanners such as OddsJam and RebelBetting find arbs faster across many books, for a subscription.

Start with the calculator

Enter two prices in the arbitrage calculator and it will tell you whether they're an arb and how to split the stake.