No-Vig Calculator: How to Find True Odds and Implied Probabilities in 2026
A no-vig calculator strips out the sportsbook’s built-in margin (the "vig" or overround) from betting odds, revealing the true implied probabilities and letting you compare value across markets. By removing the vig, you get a more accurate sense of what the market actually thinks the chances are—and a fair baseline to compare odds, arbs, or prediction market prices.
What Is a No-Vig Calculator?
A no-vig calculator is a tool that takes the odds offered by a sportsbook (which always include a margin for the house) and removes that built-in edge to show the underlying true probabilities. This is crucial for anyone comparing odds across venues or trying to understand if an opportunity really exists once all costs are accounted for.
For example, if a sportsbook lists both sides of a coin flip at -110 (American odds), the implied probabilities add up to more than 100%—the excess is the vig. A no-vig calculator tells you what the fair price would be if there were no edge for the house.
Why Use a No-Vig Calculator?
- Compare odds across sportsbooks fairly: Each book sets its own margin; stripping that out lets you see who’s actually offering the best line.
- Benchmark prediction market prices: Prediction markets like Kalshi and Polymarket quote prices as probabilities, but comparing them to sportsbook odds only makes sense after removing the vig from the latter.
- Spot potential arbitrage opportunities: True cross-venue edges only exist after accounting for all fees and vig.
- Get a sense of market consensus: No-vig probabilities are the market’s "real" estimate of an outcome’s likelihood.
How Does a No-Vig Calculator Work?
Let’s walk through a worked example for a two-way market—the most common scenario in US sports betting.
Suppose a sportsbook lists these odds for an NFL game:
| Team | American Odds | Decimal Odds |
|---|---|---|
| Eagles | -120 | 1.83 |
| Cowboys | +105 | 2.05 |
Step 1: Convert Odds to Implied Probabilities
For negative American odds (favorite):
[ \text{Implied Probability} = \frac{\text{Odds}}{\text{Odds} + 100} ]
So for -120: ( \frac{120}{120+100} = \frac{120}{220} = 54.55% )
For positive American odds (underdog):
[ \text{Implied Probability} = \frac{100}{\text{Odds} + 100} ]
So for +105: ( \frac{100}{105+100} = \frac{100}{205} = 48.78% )
Total: 54.55% + 48.78% = 103.33%
That extra 3.33% is the vig/overround.
Step 2: Remove the Vig to Find No-Vig Probabilities
Divide each implied probability by the total overround:
- Eagles: ( 54.55% \div 103.33% = 52.78% )
- Cowboys: ( 48.78% \div 103.33% = 47.22% )
These now add to 100%. This is what a no-vig calculator outputs: the "fair" probabilities before the sportsbook’s margin.
Step 3: Convert Back to No-Vig Odds
For decimal odds:
[ \text{Decimal Odds} = \frac{1}{\text{No-Vig Probability}} ]
- Eagles: 1 / 0.5278 = 1.89
- Cowboys: 1 / 0.4722 = 2.12
For American odds:
- Eagles: -100 / (1.89 - 1) = -112
- Cowboys: (2.12 - 1) × 100 = +112
The sportsbook’s -120/+105 lines become -112/+112 with no vig.
Example Table: Vig, No-Vig Probabilities, and No-Vig Odds
| Team | Book Odds (Am) | Implied Prob. | No-Vig Prob. | No-Vig Odds (Dec) | No-Vig Odds (Am) |
|---|---|---|---|---|---|
| Eagles | -120 | 54.55% | 52.78% | 1.89 | -112 |
| Cowboys | +105 | 48.78% | 47.22% | 2.12 | +112 |
Why Does the Vig Matter for Arbitrage and Prediction Markets?
When ArbMonster scans for opportunities between sportsbooks and prediction markets, it always removes the vig from sportsbook lines to make an apples-to-apples comparison with market prices on Kalshi and Polymarket. This is crucial, since prediction markets quote prices in probabilities and charge explicit taker fees (see venue details), while sportsbooks embed their margin in the odds themselves.
ArbMonster’s vig calculator automates this process, supporting American, decimal, and fractional odds, and even three-way markets (like soccer 1X2). For each opportunity, the system shows net edge after all fees and margins, at fillable size—see it in action on the live dashboard.
Three-Way No-Vig Calculation: A Soccer Example
Suppose a sportsbook lists:
| Result | American Odds | Decimal Odds |
|---|---|---|
| Home Win | +180 | 2.80 |
| Draw | +220 | 3.20 |
| Away Win | +140 | 2.40 |
Convert to implied probabilities:
- Home Win: 100 / (180+100) = 35.71%
- Draw: 100 / (220+100) = 31.25%
- Away Win: 100 / (140+100) = 41.67%
- Total = 108.63%
Remove the vig:
- Home Win: 35.71% / 108.63% = 32.88%
- Draw: 31.25% / 108.63% = 28.78%
- Away Win: 41.67% / 108.63% = 38.34%
Convert to no-vig odds:
- Home Win: 1 / 0.3288 = 3.04 (decimal), +204 (American)
- Draw: 1 / 0.2878 = 3.47 (decimal), +247 (American)
- Away Win: 1 / 0.3834 = 2.61 (decimal), +161 (American)
This lets you see which result the market really thinks is likeliest—without the house edge.
Key Takeaways
- A no-vig calculator removes the sportsbook’s margin from odds, showing the true implied probabilities.
- This lets you compare prices fairly across sportsbooks, prediction markets, and arbitrage opportunities.
- The process works for all odds formats (American, decimal, fractional) and for two-way or three-way markets.
- ArbMonster’s vig calculator and no-vig calculator automate these steps, and the live scanner always measures edges net of vig and fees.
- True cross-venue opportunities only exist after accounting for all fees (see venue details) and margins.
FAQ
Q: What is a no-vig calculator and why use it?
A no-vig calculator strips the sportsbook’s margin (vig) from odds, revealing the "true" probabilities implied by the betting market. This allows for apples-to-apples comparisons with prediction market prices or other sportsbooks, and is essential for evaluating arbitrage opportunities. Without removing the vig, you can’t accurately compare odds across different platforms.
Q: How do I use a no-vig calculator for a three-way market (like soccer 1X2)?
For three-way markets, convert all odds to implied probabilities, sum them, then divide each by the total to get no-vig probabilities. Finally, convert those probabilities back to odds if needed. Many calculators (including ArbMonster’s no-vig tool) automate this for you.
Q: Does a no-vig calculator account for prediction market fees?
No; a no-vig calculator only removes the sportsbook’s built-in margin. Prediction market fees (like Kalshi’s or Polymarket’s taker fees) are separate and must be deducted from potential returns when comparing cross-venue opportunities. ArbMonster’s live scanner shows all numbers net of sportsbook vig and prediction market fees.
Q: Where can I find a good free no-vig calculator in 2026?
You can use ArbMonster’s no-vig calculator for free, supporting all major odds formats and both two-way and three-way markets. The site also provides live comparisons of sportsbook and prediction market lines, all net of vig and fees.
ArbMonster is a data service. Nothing here is financial or betting advice; markets carry risk, venues have age and jurisdiction restrictions, and you are responsible for verifying everything before acting.