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Arbitrage & Surebet Finder

The OddsFantasy arbitrage finder scans bookmakers and Polymarket for arbitrage bets: markets where backing every outcome at the best available odds returns more than your total stake whichever outcome wins. Each row shows the event, the market, the bets that make up the arb and its ROI, and the built-in calculator splits your stake so every outcome pays the same. Arbitrage bets are also known as surebets or arbs, so this is the tool many bettors call a surebet finder.

What is an arbitrage bet?

An arbitrage bet (arb) appears when bookmakers or prediction markets disagree enough on a market that the implied probabilities of all its outcomes add up to less than 100%. Staking each outcome in proportion to its implied probability then pays the same amount whichever outcome wins, and that payout is larger than the total stake.

An arb exists when: 1 ÷ odds A + 1 ÷ odds B (+ …) < 1
Stake on an outcome = total stake × (1 ÷ its odds) ÷ (sum of 1 ÷ odds)
ROI = 1 ÷ (sum of 1 ÷ odds) − 1

Odds 2.10 and 2.05 with a $1,000 total stake:
1 ÷ 2.10 + 1 ÷ 2.05 = 0.9640, so it is an arb
Stakes: $493.98 and $506.02, payout $1,037.35 either way
Profit: $37.35, ROI 3.73%

How to use the arbitrage finder

  • Sort by ROI to see the biggest arbs first, or by event date or bet age.
  • Open the calculator on a row to split your total stake across its bets.
  • Place every leg quickly: an arb closes as soon as one of its prices moves.
  • Add the bets to the bet tracker to record the result.

What can go wrong with an arb?

  • A price moves or a bet is rejected before you place every leg, leaving you with an unhedged position.
  • Markets can settle differently, for example on extra time, void rules or player withdrawals. Check that every leg settles the same way, especially between a bookmaker and Polymarket, whose resolution rules are written differently.
  • Stake limits can cap how much you can place at the arb price.
  • Bookmakers may restrict accounts that bet arbs regularly.
  • Commission and trading fees reduce the ROI.

Arbitrage betting FAQ

What is a surebet?

A surebet is another name for an arbitrage bet: a set of bets on every outcome of an event, at different bookmakers or on Polymarket, whose odds guarantee a profit whichever outcome wins. The finder lists live surebets with their ROI and the stake for each bet.

Is arbitrage betting legal?

Arbitrage betting is generally legal where sports betting is legal, but bookmakers' terms often let them limit or close accounts they suspect of arbing. Check the rules that apply where you live and on each site you use.

What ROI is normal for an arb?

Most arbs return a small percentage of the total stake. An unusually large ROI is often a sign of a stale price or of a market that settles differently, so check both before you bet.

Can I find arbs between Polymarket and bookmakers?

Yes. The finder lists arbs across bookmakers and Polymarket. Polymarket prices are shares priced between $0 and $1, so a price of $0.40 is equivalent to decimal odds of 2.50 (1 ÷ 0.40).

Can I check an arb without the finder?

Yes. Enter the odds for each outcome in the arbitrage calculator to see whether they form an arb and how to split your stake.

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