Glossary

What is implied probability in betting odds?

Last updated 2026-07-04

Implied probability is the win chance embedded in a betting price: 1 divided by the decimal odds. Decimal odds of 2.50 (+150 American) imply 40%. Because prices include vig, a single book's implied probabilities across a market sum to more than 100%.

Every odds format is a probability wearing a costume. American -110 is decimal 1.909 is implied 52.4%. Converting everything to probability is the first step of any quantitative workflow, because probabilities can be compared, devigged, and multiplied where prices cannot.

The vig caveat matters: implied probability from one book overstates true probability by the margin. To recover the market's honest estimate, devig the full market (see no-vig fair odds). A bet is +EV when your estimate of true probability exceeds the offered implied probability.

Convert any single price with the odds converter; it shows American, decimal, fractional, and implied probability simultaneously.

Compute it with the API

curl "https://api.theoddsapi.com/odds/?sport_key=basketball_nba&oddsFormat=decimal" \
  -H "x-api-key: YOUR_API_KEY"

Decimal format makes the conversion one division in your code: probability = 1 / price. Free key in minutes.