How the No-Vig Fair Odds Calculator Works

Overview

Sportsbooks bake margin into market prices. The No-Vig Fair Odds Calculator removes that margin to estimate fair probabilities and fair prices for comparison.

The Formula

FairProb(A) = ImpliedProb(A) / (ImpliedProb(A) + ImpliedProb(B))

This proportional method is a common starting point. Other devig methods can produce different fair prices, especially in favorite-longshot markets.

When To Use It

Use it to understand how much vig is in a market, compare books, and feed a fair-price estimate into EV or Kelly calculations. The result is a model input, not proof that a candidate bet is profitable.

Worked Example

A market at -120 / +100 sums above 100%. Removing vig estimates the favorite near 52.2%, or around -109 fair price. A better offered number may be a candidate worth reviewing.

Common Mistakes

  • Using one book as the entire fair market.
  • Forgetting to devig three-way markets.
  • Mixing devig methods between comparisons.
  • Treating fair odds as guaranteed truth.

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