Sports Betting Vig Calculator: How to Calculate and Interpret Sportsbook Vigorish in 2026
A sports betting vig calculator determines the hidden cost (vigorish) built into sportsbook odds—typically expressed as a percentage of the total bet amount. To use one, you enter the odds for each side of a bet, and the calculator outputs the sportsbook's hold (vig), showing how much the book expects to retain from all wagers regardless of outcome. This is essential for understanding your true cost and comparing value across venues.
What Is Vig in Sports Betting?
Vig, short for "vigorish," is the built-in edge sportsbooks add to every bet. It's the reason standard bets like -110/-110 on both sides of an NFL spread don't pay even money. The vig ensures the book makes a profit over time, regardless of which side wins. This overround is invisible unless you calculate it directly from the odds.
Learn more about vig in our glossary.
How a Vig Calculator Works
A vig calculator takes the odds for each outcome—moneyline, spread, total, or any two-sided bet—and converts them to implied probabilities. When you sum those probabilities, they'll usually add up to more than 100%: the difference is the vig. The calculator then expresses this as a percentage of the total pool or as a "hold" per $100 wagered.
ArbMonster's vig calculator tool does this automatically for any odds format (American, decimal, fractional) and any number of outcomes.
The Vig Formula (Two Outcomes)
For a simple two-sided market (e.g., Team A -110 vs. Team B -110):
- Convert odds to implied probability for each side:
- For negative American odds (e.g., -110):
$\text{Probability} = \frac{|\text{Odds}|}{|\text{Odds}| + 100}$ - For positive American odds (e.g., +120):
$\text{Probability} = \frac{100}{\text{Odds} + 100}$
- For negative American odds (e.g., -110):
- Sum the probabilities.
- Vig = (Sum of probabilities) - 1 (as a decimal), or (Sum of probabilities - 100%) as a percentage.
Worked Example: Calculating the Vig on a Standard Spread
Let's use a real-life-ish NFL spread:
| Side | Odds | Implied Probability |
|---|---|---|
| Team A | -110 | 52.38% |
| Team B | -110 | 52.38% |
| Total | 104.76% |
Step 1: Convert odds to implied probability:
- Team A: $\frac{110}{110+100} = 0.5238$
- Team B: $\frac{110}{110+100} = 0.5238$
Step 2: Add probabilities: 0.5238 + 0.5238 = 1.0476 (104.76%)
Step 3: Vig = 104.76% - 100% = 4.76%
So the sportsbook's hold is 4.76%—for every $100 bet on both sides, the book expects to keep $4.76 over the long run.
Vig for Multi-Outcome Markets
For markets with more than two possible outcomes (like futures or prop bets), the formula generalizes:
- Convert each side's odds to implied probability.
- Sum all probabilities.
- Vig = (Sum of probabilities) - 1 (or - 100%).
Example:
Suppose a three-outcome soccer match:
| Outcome | Odds | Implied Probability |
|---|---|---|
| Home Win | +150 | 40.00% |
| Draw | +220 | 31.25% |
| Away Win | +180 | 35.71% |
| Total | 106.96% |
Vig = 106.96% - 100% = 6.96%
You can run these numbers instantly with ArbMonster's vig calculator, which supports any number of outcomes.
Why Vig Matters for Bettors and Arbitrageurs
Vig is not an explicit fee—it's embedded in the odds. The higher the vig, the worse the value for bettors. For arbitrageurs scanning for opportunities between sportsbooks and prediction markets (like Kalshi and Polymarket), knowing the true vig is essential for precise edge calculations. ArbMonster measures real sportsbook vig from 20+ US books every 15 minutes, always net of all fees and at fillable size.
For example, if one book offers -105/-105 (2.44% vig) and another -115/-115 (6.98% vig), the lower-vig book is always better for the same bet. Prediction markets charge explicit taker fees instead of hidden vig—see the venues page for detailed fee schedules.
Table: Vig by Common Odds Formats
| Odds (Both Sides) | Implied Prob. Each | Total Prob. | Vig (%) |
|---|---|---|---|
| -110 / -110 | 52.38% | 104.76% | 4.76 |
| -105 / -105 | 51.22% | 102.44% | 2.44 |
| -115 / -115 | 53.49% | 106.98% | 6.98 |
| Even / Even (+100) | 50.00% | 100.00% | 0.00 |
Key Takeaways
- Vig (vigorish) is the hidden cost in sportsbook odds, usually 2–7% on major markets.
- A vig calculator instantly shows the sportsbook's hold for any set of odds and any number of outcomes.
- Lower vig means better value for bettors and higher edges for arbitrageurs.
- Unlike sportsbooks, prediction markets like Kalshi and Polymarket charge explicit taker fees instead of embedded vig.
- ArbMonster offers a live, net-of-fee view of sportsbook and prediction market opportunities, measuring real vig across 20+ venues.
FAQ
Q: What is a sports betting vig calculator?
A sports betting vig calculator is a tool that takes sportsbook odds (in any format) and tells you the hidden margin, or hold, the book is charging. It translates odds into implied probabilities, sums them, and shows how much above 100% the total is—that's the vig.
Q: Why does the vig matter in sports betting?
Vig is the main source of profit for sportsbooks and the main cost for bettors. It reduces payouts and makes it harder to profit. By calculating the vig, you can compare which sportsbook offers better value or spot arbitrage opportunities.
Q: How do I use a vig calculator for three-way bets or futures?
Just enter the odds for all possible outcomes—most calculators (like ArbMonster's) support any number of selections. The tool will sum the implied probabilities and show the total vig, regardless of how many sides there are.
Q: Is there a difference between explicit fees and vig?
Yes. Sportsbooks build their fee (vig) into the odds, so it's not visible on your bet slip. Prediction markets like Kalshi and Polymarket charge explicit taker fees on trades instead. Both reduce your net return, but they're calculated and applied differently.
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.