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Odds to probability calculator

Convert a prediction-market price, American odds, decimal odds or fractional odds into implied probability, and compare against your own estimate. Runs in your browser; nothing is sent anywhere.

Live markets

Most-traded open markets right now. Click "Use" to load the YES price (ask, or last trade if there is no ask) into the calculator.

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How it works

Contract price: a YES contract paying $1 priced at 62¢ implies 62%.
American: negative odds −X imply X/(X+100); positive +X imply 100/(X+100).
Decimal: 1/odds. Fractional a/b: b/(a+b).
Expected value per $1 contract = your probability − price − fee. Sportsbook odds include the bookmaker's margin, so implied probabilities on both sides add to more than 100%.

Not financial advice. See also: State of Kalshi stats · Glossary