No Vig Calculator (Devig) — Fair Odds from American or

What this calculator does

Sportsbooks don't publish probabilities — they publish prices. Every price has the book's margin baked in, called the vig (vigorish, juice, hold, overround). On a standard -110 / -110 NFL spread, the book is taking roughly 4.76% off the top: bet $100 to win $90.91 per side, lose either way and the book pockets the difference. The no-vig price strips that margin out so you can compare the book's true probability estimate against your own model.

Worked example: NFL spread

Suppose the Chiefs are -3.5 (-110) against the Bills at +3.5 (-110). Both sides imply 52.38% probability. Their sum is 104.76% — the book's overround. The vig is 4.76%.

Devigging proportionally: each fair probability is 52.38 / 104.76 = 50.00%. The fair line both ways is +100 (decimal 2.000). That makes sense — at -110 / -110 the book is implicitly telling you the spread is a perfect 50/50. If your model says the Chiefs are 53% to cover, you have a 3% edge against the book's true probability estimate, which after a Kelly stake sizing becomes a real wager — not the 50.62% edge a naive read of the would suggest.

Why vig matters more than picks

Most bettors lose because they bet - markets at vig that's too high to overcome. A 55%-accurate cap on a -110 spread is +3% EV; the same cap at -120 is +0.4% EV; the same cap at -130 is negative. Shopping books for the lowest-vig price on the same line is the highest-leverage thing a serious bettor does — every point of vig you save is one point of edge you keep.

FAQ

What is vig (vigorish) in sports betting? +

Vig is the margin a sportsbook builds into both sides of a market so it profits regardless of which side wins. On a standard NFL spread priced -110 / -110, the implied probabilities of the two sides sum to about 1.0476 — that 4.76% overround is the vig. The book keeps roughly $4.76 of every $100 wagered when action is balanced.

How do you remove the vig from American odds? +

Convert each American line to its implied probability, sum the implied probabilities across all outcomes (the total exceeds 1.0 because of the vig), then divide each implied probability by the total. The result is the no-vig (fair) probability for that outcome. Multiply through to get fair decimal odds or American odds.

Proportional vs. power devig — which method should I use? +

Proportional (dividing each implied probability by the total) is the standard method and works well for low-juice two-way markets like NFL or NBA spreads. Power devig (raising each implied probability to an exponent that normalizes the sum) is better for heavy-juice or many-outcome markets — three-way soccer 1X2, futures markets, and player props where favorites carry disproportionate juice. Pick proportional by default; switch to power when you notice favorites looking too cheap after a proportional devig.

What is a "fair" odds price? +

A fair odds price is what the bet would be priced at if the sportsbook took zero margin — pure 50/50 split of the implied probability. Comparing fair odds across two or more books is the foundation of arbitrage and middling; comparing your model's probability against the fair odds tells you whether you have an edge net of the vig.

Why does the no-vig calculator show different numbers than the book's "true odds"? +

Books don't publish their own fair-price estimate — they publish prices designed to balance action and capture vig. Multiple books often disagree on the true probability of an event by 1–3 points. Devigging consensus prices across the sharpest books (Pinnacle, Circa, Bookmaker) typically gets you within 1 percentage point of the market's true probability estimate.

Can I use this for parlays or correlated markets? +

No — this tool devigs a single market with mutually exclusive outcomes (one side wins, the others lose). For parlay expected value, use the parlay EV calculator. For correlated markets (team total + game total, alt spread + ML), no-vig assumptions break down and you need a joint-probability model.