No-vig calculator: remove the vig from any two-way odds
Short answer: Convert each side's American odds to an implied probability, then divide each by their sum. For -120 and +100 that is 54.55% and 50.00%, 104.55% together, so the no-vig probabilities are 52.17% and 47.83% and the fair prices are -109 and +109. Enter any two prices to get the fair odds and the book's margin.
| Side A | Side B | |
|---|---|---|
| Price | -120 | +100 |
| Implied probability (with vig) | 54.55% | 50.00% |
| No-vig probability | 52.17% | 47.83% |
| Fair price (American) | -109 | +109 |
| Fair price (decimal) | 1.917 | 2.091 |
The two prices add up to 104.55%: an overround of 4.55 points, a bookmaker margin (hold) of 4.35%.
Showing a worked example. Enter your own numbers above; the result's link can be shared.
How the calculation works
- Convert each price to an implied probability. Negative odds: odds ÷ (odds + 100), using the absolute value. Positive odds: 100 ÷ (odds + 100). So -120 → 120 ÷ 220 = 54.55%, and +100 → 100 ÷ 200 = 50.00%.
- Add them. The total is above 100% because of the vig: here 104.55%.
- Divide each side by the total: 54.55 ÷ 104.55 = 52.17% and 50.00 ÷ 104.55 = 47.83%. Those are the no-vig (fair) probabilities.
- Convert back to odds: above 50% → -100 × p ÷ (1 - p); below 50% → 100 × (1 - p) ÷ p. Here -109 and +109.
This is the multiplicative (proportional) method, the most common one. Other methods (additive, power, Shin) shift a little more of the margin onto the longer price; on two-way prices near even money the difference is a fraction of a percentage point.
What it's for
A fair price tells you what a bet is worth before the bookmaker's cut. Bettors usually remove the vig from a sharp book such as Pinnacle and compare the result with what a retail book like DraftKings offers on the identical line. If the retail price pays more than the fair price, the bet is +EV by that estimate (see the EV calculator). It is an estimate, not a guarantee: OpenSlate's research found the comparison held up on NBA Unders and did not on Overs (Trap Overs) or on NFL props.
Typical margins on player props
Player props carry more vig than main lines. -110 / -110 is a 4.76% margin; prop pairs such as -125 / -105 run 5.5% or more. Today's median margin at DraftKings and Pinnacle is measured from tonight's lines.
Other tools: Expected value (EV) calculator for sports bets · Odds converter: American, decimal, fractional and implied probability. Guides: Learn.
Arithmetic only, not betting advice. 21+. Problem gambling? Call 1-800-GAMBLER.