Direct Answer
Implied probability is the probability of an outcome encoded mathematically in a betting price. It is the bridge between price and probability and the basis of every EV calculation. Implied probability includes the sportsbook's margin and overstates true probability.
Key Takeaways
- Every price is a probability statement.
- Implied probability includes vig.
- Both sides sum to more than 100% by the hold.
- De-vig by proportional normalization for cleaner comparisons.
Formulas
American negative: implied = (–odds)/(–odds + 100). American positive: implied = 100/(odds + 100). Decimal: implied = 1/decimal. Fractional: implied = denom/(num + denom).
Why both sides sum over 100%
A –110/–110 market implies 52.38% on each side — 104.76% total. The 4.76% overround is the book's hold. To recover the market's estimate of true probability, divide each side by the overround. –110/–110 de-vigs to 50%/50%.
Frequently asked questions
Which de-vig method should I use?+
Proportional is the standard. Power and Shin methods adjust for known biases in specific sports but the difference is small in most markets.
Educational only. Not wagering, financial, or legal advice. See our editorial policy.