Free prediction-market calculators
Six free tools every Polymarket and Kalshi trader needs — convert odds, remove the vig, hedge a position, find risk-free arbs, and size your bets. Instant, exact, and no signup.
Hedging Calculator
Find the exact hedge bet to lock in a guaranteed profit whichever way it resolves.
Open calculatorNo-Vig Fair Odds
Strip the bookmaker margin to reveal the fair odds and true probability of any line.
Open calculatorOdds Converter
Convert American, decimal & fractional odds to implied probability and Polymarket price.
Open calculatorArbitrage Calculator
Detect a risk-free arb and get the exact stakes to lock a guaranteed profit.
Open calculatorExpected Value
Enter your probability vs the market price to see if a bet is +EV and your edge.
Open calculatorKelly Criterion
Get your optimal bet size from your edge and bankroll, with safer fractional-Kelly options.
Open calculatorWhy we built these
Prediction markets like Polymarket price everything as a probability — a share at 65¢ means a 65% chance. That makes them a natural fit for the classic betting-math tools, but most calculators online speak sportsbook, not prediction market. Ours work in whichever format you like (American, decimal, or a price in cents) and are framed for how Polymarket and Kalshi actually work.
Want the tools that do this automatically — scanners, trackers, bots and alerts? Browse the full Polymarket tools directory, ranked weekly by real traders.