Prediction Market Calculator
Convert between odds formats, calculate payouts on Kalshi and Polymarket contracts, and check the expected value of a trade. Built for prediction market traders who want the math done once, cleanly.
Convert between contract price, implied probability, American odds, and decimal odds. Change any field and the others update automatically.
Enter a contract price and number of shares to see total cost, profit if the contract resolves YES, and return on investment. Contracts settle at $1 per share. If the contract resolves NO, you lose the full cost.
Market price is what the crowd thinks. Your probability is what you think after doing the work. Expected value is the difference, applied to your stake. Positive EV means the trade makes money on average over time. Negative EV on YES often means there is value on the NO side instead.
See a Kalshi contract at 54¢? That is 54% implied probability, roughly −117 in American odds. The odds converter turns any format into any other format instantly.
Thinking about buying 100 shares at 54¢? The payout calculator shows you would pay $54 upfront and make $46 profit if it resolves YES. If it resolves NO, the $54 is gone. Size accordingly.
Think the true probability is closer to 62%? The expected value calculator tells you the YES trade is worth +$14.81 on a $100 stake, or +14.81% ROI. Anything above zero is a positive EV trade on YES. Below zero means the market disagrees with your estimate. You might be wrong, or there might be value on the NO side at the inverse price.
For active CS2 picks with full reasoning, see the Kalshi CS2 hub. For the full tools hub see the tools page.
A Kalshi contract price in cents equals the implied probability as a percentage. A 54¢ contract equals 54% implied probability. If probability is 50% or higher the odds are negative (favorite). If probability is below 50% the odds are positive (underdog). The converter above handles both directions automatically.
A positive expected value trade is one where your estimated probability of the YES outcome is higher than the market price. If a contract trades at 54¢ and you estimate the true probability at 62%, you have an 8 percentage point edge and a +14.81% expected ROI on your stake. Over many trades with the same edge, you make money on average. If your estimate is lower than the market price, there may be value on the NO side instead.
Kalshi contracts settle at $1 per share if YES resolves and $0 if NO resolves. If you buy 100 shares at 54¢, you pay $54 upfront. A YES resolution returns $100 total, which is $46 profit on your $54 stake. A NO resolution returns $0 and you lose the $54. Trading fees are applied per contract and reduce net profit slightly.
Yes. Kalshi charges a per-contract trading fee that scales with contract price and order size. Fees are highest on contracts priced near 50¢ (typically 1 to 2¢ per share for takers) and drop toward zero on contracts priced near 1¢ or 99¢. Maker orders (resting limit orders) are charged at a lower rate. Polymarket currently charges no trading fees. This calculator shows gross profit before fees.
Yes. Polymarket uses the same contract pricing structure as Kalshi where prices range from roughly 1¢ to 99¢ per share and contracts settle at $1 equivalent (paid in USDC). The calculator works identically for both platforms.
The Game of Skill prediction market calculator converts between contract prices, implied probabilities, American odds, and decimal odds. Built for Kalshi and Polymarket traders on CS2 and other events. Includes payout calculator for estimating contract profit and ROI, plus expected value calculator for identifying positive EV trades. All calculations are gross, before platform trading fees. For CS2-specific prediction market picks see the CS2 prediction markets page. For Kalshi platform review see the Kalshi review. For Polymarket review see the Polymarket review.