Glossary / Betting math / Implied probability
A ParlayAPI glossary entry

Implied probability

Implied probability is the win probability that an odds price implies. For American odds, positive prices convert as 100/(price+100) and negative prices as |price|/(|price|+100). For decimal odds it is simply 1/decimal. Implied probability always includes the bookmaker's vig until you devig it.

Conversion cheatsheet

# American odds -> implied probability
        +130  ->  100 / (130 + 100)   = 43.5%
        -150  ->  150 / (150 + 100)   = 60.0%
        +100  ->  100 / 200           = 50.0%
        
        # Decimal odds -> implied probability
        2.30  ->  1 / 2.30            = 43.5%

Everything in betting math is downstream of this conversion: vig is an implied-probability sum minus 1, devigging is normalizing implied probabilities, and a +EV bet is one where your estimate of the true probability beats the implied one.

Where it shows up in ParlayAPI

ParlayAPI returns prices in American or decimal format (your choice via the odds-format parameter, matching the-odds-api conventions), and either converts to implied probability in one line of code. See the docs for response shapes, or try a live request on the free tier - 1,000 credits/month, no card required.

Related terms

American oddsThe US-standard plus/minus odds format. Decimal oddsTotal payout per unit staked. DeviggingStrip the bookmaker margin to a fair probability. Implied sumImplied probabilities summed across a market.