Prediction Market Arbitrage Calculator
Enter the YES price on one platform and the NO price on the other, plus your stake and the days until the markets resolve.
Assumes both legs fill completely at the prices entered, that both markets resolve the same way, and that you hold to resolution. Kalshi taker fee = 0.07 × contracts × price × (1 − price), rounded up to the cent; Polymarket taker fee uses the 0.05 rate for most categories (some categories differ). Fees can change, so check each platform's current schedule. Annualised return = net edge × 365 ÷ days, not compounded. Not financial advice.
Want matching pairs found for you?
Arbitrage Agent matches markets across Kalshi and Polymarket and shows each one in a live feed with a step-by-step guide for both legs. You place the orders yourself.
Start with the Starter plan →How the numbers are worked out
Buying YES on one platform and NO on the other for the same event pays $1 per contract whichever side wins. The cost is the two prices added together, plus the fees. If the cost is below $1, the difference is the edge. Contracts are whole numbers, so the calculator buys floor(stake ÷ (YES + NO)) of each.
The Kalshi fee follows the published formula, 0.07 × contracts × price × (1 − price), rounded up to the next cent for the order. The derivation is in how Kalshi fees are calculated.
The annualised return matters because the capital stays locked until both markets resolve. A small edge over many months can be a low yearly figure, which is covered in capital lockup and settlement time. For a real snapshot, see what our scanner saw in 24 hours.
A positive number here is not a guarantee. Check that both markets resolve on the same terms, as explained in resolution mismatch.
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© 2026 Arbitrage Agent. Not financial advice. Trading involves risk of loss.