Kalshi Arbitrage Calculator

An arb exists when you can cover every outcome for a combined cost under the payout. On a binary market that means buying YES on one venue and NO on another so the two prices sum to under $1 (under 100¢).

Example: Kalshi has YES at 60¢, Polymarket has NO at 38¢. Combined cost is 98¢ to guarantee a $1 payout — a 2% risk-free edge before fees. The calculator sizes each leg so you collect the same total whichever way it resolves.

Each leg here has its own format selector, because the two sides of a cross-platform arb often live on different kinds of venues — a prediction market quoting cents and a sportsbook quoting American odds. Under the hood everything converts to decimal odds, then the arb test is the same: if the implied probabilities sum to less than 100%, there's an edge.

To translate a single price yourself, use the prediction market odds converter.

This calculator shows the arb before costs. Real execution faces the prediction market trading fee, the sportsbook's spread, withdrawal frictions, and the risk that a price moves while you're placing the second leg. A 1% arb often disappears once those are counted — and the account-limiting risk on the sportsbook side is the same whether the edge is 1% or 5%. Estimate the fee on each prediction-market leg with the Kalshi fee calculator before committing.