Fair Odds Calculator
Enter the price on both sides of a market. We scale the implied chances back to 100% to estimate a fair, no-margin price for each side.
Sportsbook odds include margin. This calculator removes the estimated margin to produce a fair-market probability estimate. It uses the multiplicative de-vig method: implied chances are scaled proportionally until they sum to 100%. The output is an estimate of the fair market price, not a prediction of the outcome.
Example
A standard point spread is priced -110 / -110. Each side implies 52.38%, so the two sides add to 104.76%.
That extra 4.76% is the estimated sportsbook margin. Scaling both back to 100% gives an estimated fair probability of 50% per side, or estimated fair odds of +100.
What the results mean
- Implied probability (with margin)
- The break-even win rate the posted price demands. Both sides together add to more than 100% because the book's margin is included.
- Estimated sportsbook margin
- How much the two prices exceed a 100% market. The bigger this number, the more the pricing works against you.
- Estimated fair probability
- The implied chance after the margin is removed proportionally across both sides.
- Estimated fair odds
- The price that estimated fair probability corresponds to. If a book pays more than this, the price is in your favour.
Frequently asked questions
Keep reading
- Fair odds vs sportsbook odds — what the gap actually represents
- How sportsbook vig works — where the margin comes from
- Parlay EV Calculator — price a full ticket against fair odds
Want to evaluate multiple legs at once?
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