Vig Calculator (Decimal Odds): How to Find Sportsbook Edge Using Decimal Prices in 2026
A vig calculator for decimal odds lets you determine how much edge (or "hold") a sportsbook is charging on a betting market, by converting the posted decimal prices into implied probabilities and summing them. If the total exceeds 100%, the difference is the vig. You can also use a no-vig calculator to find the "fair" (zero-edge) probabilities.
How Vig Works With Decimal Odds
Decimal odds are the most straightforward way to display betting prices: a decimal like 1.91 means you receive $1.91 for every $1 wagered, including your stake. In a fair market (no vig), the sum of implied probabilities for all outcomes equals 100%. Sportsbooks build in a margin so this sum is higher; the difference is called the vig or overround.
The basic formula for implied probability from decimal odds is:
Implied probability = 1 / Decimal odds
For example, decimal odds of 1.91 imply a probability of 1 / 1.91 ≈ 52.36%.
Step-by-Step: Calculating Vig From Decimal Odds
Let's work through a real-ish example. Suppose an NFL game has these mainline decimal odds:
| Outcome | Decimal Odds |
|---|---|
| Team A | 1.91 |
| Team B | 1.91 |
1. Convert Odds to Implied Probabilities
- Team A: 1 / 1.91 ≈ 0.5236 (52.36%)
- Team B: 1 / 1.91 ≈ 0.5236 (52.36%)
Total implied probability = 52.36% + 52.36% = 104.72%
2. Calculate the Vig (Overround)
- Vig = (Sum of implied probabilities) – 100%
- Vig = 104.72% – 100% = 4.72%
This means the sportsbook is charging a 4.72% edge on this market. This matches what ArbMonster measures as typical for standard -110/-110 lines (the decimal equivalent is 1.91/1.91).
3. Use a Vig Calculator for Any Decimal Odds
If the odds are different (say, 1.80 vs 2.05):
| Outcome | Decimal Odds |
|---|---|
| Team A | 1.80 |
| Team B | 2.05 |
- Team A: 1 / 1.80 ≈ 0.5556 (55.56%)
- Team B: 1 / 2.05 ≈ 0.4878 (48.78%)
- Total: 55.56% + 48.78% = 104.34%
- Vig = 104.34% – 100% = 4.34%
You can check these calculations yourself using the ArbMonster no-vig calculator or vig calculator.
Why Vig Matters for Arbitrage and Expected Value
The vig is the built-in cost to anyone betting at posted lines. For arbitrage, it's crucial to know the true odds—without vig—to spot real opportunities between markets or sportsbooks. Vig also affects expected value (EV); the higher the vig, the harder it is to find positive-EV bets.
ArbMonster measures the real vig of 20+ US sportsbooks every 15 minutes, net of all fees, and displays cross-venue opportunities after accounting for this margin. Its live dashboard lets you see how much edge is present in each market.
Table: Vig for Common Decimal Odds Combinations
| Odds 1 | Odds 2 | Implied Prob 1 | Implied Prob 2 | Total (%) | Vig (%) |
|---|---|---|---|---|---|
| 1.91 | 1.91 | 52.36% | 52.36% | 104.72 | 4.72 |
| 1.80 | 2.00 | 55.56% | 50.00% | 105.56 | 5.56 |
| 1.95 | 1.95 | 51.28% | 51.28% | 102.56 | 2.56 |
| 2.10 | 1.76 | 47.62% | 56.82% | 104.44 | 4.44 |
Removing the Vig: True (No-Vig) Probabilities
To find the "fair" or true probability for each outcome, divide each implied probability by the total sum:
- No-vig probability (for an outcome) = Implied probability / (Sum of implied probabilities)
For Team A at 1.91:
- Implied prob: 52.36%
- Sum: 104.72%
- No-vig prob: 52.36% / 104.72% ≈ 0.500 (50.00%)
So the fair odds would be 1 / 0.50 = 2.00, much better than the offered 1.91.
Key Takeaways
- Decimal odds can be quickly converted to implied probabilities using 1 / decimal odds.
- The vig is the amount by which total implied probabilities exceed 100%.
- Vig calculators help you see the true sportsbook edge and compare markets.
- Removing the vig gives you the real probabilities behind the posted prices.
- ArbMonster automates these calculations across 20+ sportsbooks and prediction markets, net of all fees.
FAQ
Q: What is a vig calculator for decimal odds?
A vig calculator for decimal odds is a tool that converts decimal betting odds into implied probabilities and sums them to reveal the sportsbook's edge (vig). It lets you see how much margin is built into the prices, and can also be used to remove the vig to find fair odds.
Q: How do you calculate vig from decimal odds?
First, convert each outcome's decimal odds to implied probability using 1 divided by the odds. Add the implied probabilities for all outcomes. The amount by which this sum exceeds 100% is the vig. For example, with 1.91/1.91, the total is about 104.72%, so the vig is 4.72%.
Q: Why does the sum of implied probabilities exceed 100%?
Sportsbooks set odds so the sum of implied probabilities is greater than 100% in order to build a margin for themselves. This overround (vig) ensures that if bets are balanced, the sportsbook profits regardless of outcome.
Q: Where can I find a free online vig calculator for decimal odds?
You can use the ArbMonster vig calculator, which works for decimal, American, and fractional odds, and also shows no-vig probabilities and fair odds for any price combination.
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.