Calculators that do the boring part
Everything here runs in your browser, needs no account, and stays free. Built because we needed them ourselves.
Live market radar
Biggest 24h movers and deepest books across Polymarket and Kalshi, pulled from the exchanges' public APIs every hour.
Open → Fees & profitPayout calculator
Payout, net profit, ROI and break-even win rate for any contract price — with Kalshi's exact fee formula applied.
Open → FormatsOdds converter
Probability ↔ contract price ↔ American ↔ decimal ↔ fractional. For anyone moving between sportsbooks and prediction markets.
Open → Position sizingKelly calculator
How much to actually put on an edge, with full, half and quarter Kelly — plus where the formula quietly betrays you.
Open → Cross-venueArbitrage checker
Does that Polymarket–Kalshi price gap survive fees? Locked profit, ROI and the minimum viable spread.
Open →Spotted a mistake or want another calculator? The fastest way to reach us is @fluxrbot on X.