Devig (De-Vigorish)

Devigging is the process of removing the bookmaker's margin (vig) from a set of odds to derive the true implied probability of each outcome. The resulting probabilities sum to exactly 100%.

Why Devigging Matters

Raw bookmaker odds always sum to more than 100% — that's the vig. If you use raw odds as probability estimates, you'll systematically underestimate every outcome's true likelihood. Devigging corrects this and reveals whether a bet has genuine positive expected value.

Devig Methods

Multiplicative (Most Common)

Divide each implied probability by the overround (sum of all implied probs).

Example: Team A 1.80 (55.6%), Team B 2.20 (45.5%). Overround = 101.1%. Fair probs: 55.6/101.1 = 55.0%, 45.5/101.1 = 45.0%.

Power Method (Most Accurate for Sharp Lines)

Finds an exponent k such that the sum of (p^k) = 1. More accurate when vig is not evenly distributed. EVBets uses the power method for all devig calculations.

Additive Method

Subtracts vig proportionally from each outcome. Simple but less precise than multiplicative.

Frequently Asked Questions