Arbitrage Calculator

Enter the two opposite outcomes from any two venues. We tell you if it's a sure bet, the exact stake split, and your guaranteed profit. Either leg can be a sportsbook line or a Polymarket / Kalshi price.

Outcome A

Outcome B

Total Stake ($)
Total you want to put across both legs
Prediction-Market Fee per Share (¢)
Applied to any leg entered in ¢. Polymarket ~0–2¢; set 0 to ignore.
Sure Bet — Arbitrage
Guaranteed profit no matter which outcome hits.
No Arbitrage
The two prices overround past 100% — backing both sides locks a small loss. Wait for a wider gap (or one venue to move).

How to Split the Stake

Stake on Outcome A
Stake on Outcome B
Guaranteed Return
Profit
ROI

Stakes are sized so the payout is identical whichever outcome hits. Round to the nearest dollar/share when you actually place — and place the leg that can move first.

Where cross-venue arbs come from

An arbitrage exists when the implied probabilities of the two opposite outcomes add up to less than 100%. Inside one sportsbook that almost never happens — the vig guarantees it. It shows up between venues that disagree, and the biggest disagreements right now are between sportsbooks and prediction markets, because they have different crowds, fees, and liquidity.

Best hunting grounds
  • Sportsbook moneyline vs Polymarket / Kalshi on the same game
  • Two prediction markets pricing the same event differently
  • A soft book lagging a sharp move
Don't forget
  • Fees and the bid/ask eat thin arbs — include the ¢ fee
  • Prices move; one leg can vanish before you fill the other
  • Limits and resolution rules can differ across venues

Find the gaps automatically

Hunting arbs by hand is slow. ZenHodl's Edge Finder watches Polymarket, Kalshi and sportsbooks side by side against one calibrated fair value — and we publish our closing-line value per sport so you can see the edge is real, not claimed.

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Free tools for sharper betting and prediction-market trading.