Implied Probability & Odds Converter

Back to the calculator. · Related: Kelly, EV, No-vig

Formulas: p = 1 / o and o = 1 / p, with o ≥ 1.01, 0 < p < 1. You can switch formats at any time — the input value converts automatically.

What is implied probability?

Implied probability converts any price format into a chance between 0–100%. It’s the bookmaker’s view of how often an outcome would occur given the odds. Converting helps you compare prices, size stakes (Kelly), and check value vs sharp markets.

Formulas: Decimal: p = 1 / o. American: p = 100 / (A + 100) for positive (e.g. +120), p = |A| / (|A| + 100) for negative (e.g. −110). Fractional: for a/b, decimal is 1 + a/b → then p = 1 / decimal.

Tip: translate offers across books and formats here, then check EV with the EV calculator or remove margin with No-vig.

FAQ

Why is the probability not an exact match to book margins?

These are raw implied probabilities. Books include margin; for “fair” probabilities remove the vig first.

Can I paste +money / fractions?

Yes. Pick the format (American / Fractional) and paste values like +120 or 10/11.

What range is valid?

Decimal odds ≥ 1.01. Probability strictly between 0 and 100.

How to use

1. Pick the Odds format (Decimal / American / Fractional).
2. Enter either Odds in the selected format or Implied probability (%).
3. The other field updates automatically. Outputs show Probability and Odds in the chosen format.

More tools: Implied probability, Arbitrage.

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