Arbs › Calculators › Arbitrage calculator

Arbitrage calculator: Polymarket and sportsbooks

Enter the best price for each outcome, in cents for Polymarket or odds for a book. The calculator nets the Polymarket fee, splits your stake, and shows the locked return.

Arbitrage calculator illustration

When two prices make an arb

If you can back every outcome of a game at prices whose implied probabilities add up to less than 100%, staking the right amount on each side returns the same payout whichever side wins. That payout is more than you staked.

With a Polymarket leg the test has to include the taker fee: price + fee per share, plus the book’s implied probability, must come in under $1. Gaps that look like profit before fees are often losses after them.

Polymarket price + r × p × (1 − p), plus 1 ÷ book decimal odds, must be under 1

Worked example

Worked example: Team A 52¢ on Polymarket, Team B +115 at a book

  1. Polymarket: 52¢ plus the 0.05 fee is 53.2¢ (decimal 1.878)
  2. Book: +115 is decimal 2.15, an implied 46.5%
  3. Total: 53.2% + 46.5% = 99.8%, under 100%
  4. $1,000 split: $533.76 on Polymarket, $466.24 at the book

$1,002.41 back either way: a 0.24% arb.

Real arbs are small and close fast. Check that both venues settle the market the same way (overtime, a walkover, a postponed game) before you stake, and confirm the price is still there.

Frequently asked questions

Can you arbitrage Polymarket against sportsbooks?

Sometimes. Polymarket and books price the same games independently, so their lines drift apart. After the Polymarket taker fee most gaps are too small, and books may limit accounts that only take arbs.

How do you calculate arbitrage stakes?

Add up 1 ÷ decimal odds for every leg. If the total is under 1, stake (total stake ÷ decimal) ÷ that sum on each leg. Every leg then pays total stake ÷ sum.

Is arbitrage betting risk-free?

No. Prices move between the two bets, a book can void or limit, and the venues can settle the same game differently. Treat it as low risk only when both legs are filled and the settlement rules match.

Does Arbs find arbs automatically?

Arbs compares Polymarket with the books on every game and shows the best venue for each side. Pro and Elite see the edges as they open.

Read the guide: Arbitrage betting between Polymarket and sportsbooks

See today’s model gaps on the live board · How Arbs prices games

More free calculators

Free betting calculators · Guides · Glossary · How Arbs works · Odds by league · Track record · Responsible gaming