Prediction Market Calculators
Free tools for smarter trading on Kalshi, Polymarket, and PredictIt.
Market Fees
Calculate Kalshi fees, payout, net profit, and ROI, then compare taker, maker, profit, and category-based fees across prediction markets.
Vig & No-Vig
Calculate the vig (juice) baked into any market and find the true fair-value probability with the overround removed. Essential for spotting mispriced contracts.
Expected Value
Determine whether a trade has positive expected value given your estimated probability and the current market price. Know your edge before you enter.
Odds Converter
Convert instantly between American odds, decimal odds, and implied probability. Works for any prediction market, sportsbook, or exchange.
Parlay
Calculate combined odds, payouts, and ROI for multi-leg prediction market parlays. Enter each leg’s price and see your blended probability and return.
Net Profit
Estimate your actual take-home after platform fees and applicable taxes. See what you really make — not just what the contract pays out.
What are prediction market calculators?
Prediction market calculators help traders quickly do the math that platforms don't surface for you — true fees, expected value, fair odds stripped of vig, and real net profit after taxes. Without these tools, you're trading on incomplete information.
Each platform has a different fee structure. Kalshi charges transaction fees on both taker and maker sides that vary by contract price. PredictIt takes 10% of profits. Polymarket currently charges nothing. A position that looks identical across platforms can have meaningfully different economics once fees are factored in. The Market Fees calculator normalizes this so you're comparing apples to apples.
The Vig and Expected Value calculators solve a different problem: market prices contain a built-in house edge that distorts the implied probabilities. No-vig math strips that out so you can see what the market actually thinks the fair probability is — and whether there's a gap between that and your own estimate.