Prediction market calculators

Short answer

Three numbers decide whether a prediction-market position is good: the implied probability you are paying, your own estimate, and the size you take. These calculators cover all three and run entirely in your browser.

Kelly calculator

Turn your estimated edge into an optimal, non-suicidal stake.

Odds & EV calculator

Convert a contract price in cents into implied probability, payout and expected value.

ROI calculator

Profit, return on stake and the hit rate you need to break even.