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True Odds Calculator
Strip sportsbook from a two-way or N-way market. Paste American odds for each outcome and get the fair probability, fair American line, fair decimal, and the book's overround in one read.
No-Vig Odds Calculator
Remove bookmaker hold from a 2-way or 3-way market, recover fair probability, and compare your model to the no-vig line.
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 implied probabilities sum to 104.76%, an overround of 4.76%. With $100 bet on each side, the book takes in $200 and returns $190.91 to the winning ticket, including its stake. It keeps $9.09, or 4.55% of the total wagered. The margin-free price strips that margin out. That produces the market's — a no-fee estimate, not a guaranteed outcome. Compare that 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. The fair probability removes the margin from the shown by the posted price.
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 +5.0% EV; the same cap at -120 is +0.8% 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. With $100 wagered on each side, the winning ticket returns $190.91 including stake. The book keeps $9.09 of the $200 wagered, or about 4.55%. Overround and the percentage of stakes kept use different denominators.
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 an entered model probability against the fair odds reports the model-market gap after removing vig.
Why does the calculator show different numbers than a book's "True odds"?
"True odds" here means a no-vig market estimate, not a guaranteed objective probability. Sportsbooks publish prices designed to balance action and capture vig, so different books can disagree. Devigging consensus prices can narrow that disagreement, but the result remains a market 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.
The bars compare each outcome's implied probability and show the total above 100% as vig.
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