Prediction market calculators
Free tools for Kalshi and Polymarket traders. Price a trade after fees, strip the vig to find a fair price, check whether a trade has positive expected value, and convert between cents, probability, American and decimal odds. Everything runs in your browser; no sign-up needed.
Fee calculator
Kalshi vs Polymarket fees for any price and size, with all-in cost and break-even.
Open calculator →No-vig calculator
Strip the overround from a set of prices to get fair, vig-free probabilities.
Open calculator →EV calculator
EV, ROI, edge and Kelly stake from a contract price and your own probability.
Open calculator →Odds converter
Convert between cents, implied probability, American and decimal odds.
Open calculator →Want live prices to plug in? The edge scanner compares the same markets across Kalshi and Polymarket, and the TPM API streams them.