Free calculators / No-vig
No-vig calculator
A bookmaker's quoted prices always add up to more than 100% implied probability — that extra margin is the vig. This strips it back out, proportionally, to estimate the market's fair probability on each side.
Fair (no-vig) probabilities
50.00%
50.00%
Book hold on this market: 4.76%
The math
fair_i = (1/odds_i) / Σ(1/odds_j) hold = (Σ(1/odds_j) − 1) × 100
Honest note: This uses the proportional method: it splits the vig evenly across every outcome. Other de-vig methods exist (e.g. Shin's model), and they can return slightly different fair probabilities, especially for longshots.
How it's computed
Each price implies a raw probability (1 / decimal odds). Summed across every outcome, that total is the market's "overround." The proportional method divides every raw implied probability by that overround, so the fair probabilities sum to exactly 100%:
Proportional de-vig
implied_i = 1 / odds_i fair_i = implied_i / Σ(implied_j)
This is the same proportional convention the pick engine itself uses as its house default for de-vigging a market — see the methodology page. It is deliberately the simpler of two documented methods: Shin's model is the other, and it corrects a bias proportional de-vig leaves on longshots. This calculator only runs the proportional version, so it stays fully explainable in one formula.
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