Understanding Vig (The Sportsbook's Edge)
Now let's talk about the invisible tax on every bet you make: the vig (short for vigorish). Understanding vig is crucial because it's the primary reason most bettors lose money.
What Is Vig?
At a true 50/50 event, like a perfectly fair coin flip, fair odds would be +100 on both sides. Bet $100, win $100. Simple.
But a typical sportsbook market might be -110 on both sides. Bet $110 to win $100.
Key Insight
At -110, the implied break-even is 52.4%, not 50%. That extra 2.4 percentage points is the sportsbook's edge (vig) expressed as probability.
How Vig Works Mathematically
When both sides of a market are -110:
| Side | Implied Probability |
|---|---|
| Over -110 | 52.38% |
| Under -110 | 52.38% |
| Total | 104.76% |
Anything over 100% is the book's edge. Here, the market vig (or "hold") is about 4.76%.
The Real Cost of Vig
Here's what this means in practice:
- Even if you're exactly as good as the market at estimating probabilities, you'll lose money over time because of the vig
- You need to be better than the market by at least 2.4 percentage points just to break even
- The average bettor loses about 4-5% of everything they wager over time
Warning
This is why casual betting is a losing proposition. The average bettor isn't trying to beat the market—they're betting for entertainment, on their favorite teams, or on gut feelings. The vig ensures they lose.
Vig Varies by Market
In spreads and totals, the vig is usually standardized (-110). In props, you see much more variation:
| Market Type | Typical Vig | Break-Even Each Side |
|---|---|---|
| Standard | -110 / -110 | 52.4% / 52.4% |
| Slightly Juiced | -120 / -105 | 54.5% / 51.2% |
| Heavily Juiced | -140 / +100 | 58.3% / 50.0% |
| One-Way Market | +110 only | Hidden (often 20-40%) |
Calculating Total Vig (Hold)
To find the total vig on any two-way market:
Market Hold (Vig)
Hold = (Implied Prob Side A + Implied Prob Side B) - 100%=(implied_A + implied_B) - 1Example: -115 / -105 Market
| Side | Calculation | Implied Prob |
|---|---|---|
| Over -115 | 115 / 215 | 53.49% |
| Under -105 | 105 / 205 | 51.22% |
| Total | 104.71% | |
| Vig | 104.71% - 100% | 4.71% |
Why Vig Matters More in Props
Props often have higher vig than main markets:
| Market Type | Typical Hold |
|---|---|
| NFL Spread | 4.5% |
| NBA Total | 4.5% |
| Standard Props | 5-7% |
| Derivative Props (TD, HR) | 15-30%+ |
| One-Way Markets | 20-40%+ |
Tip
The higher the vig, the bigger your edge needs to be. A 3% edge on a 4.5% vig market is profitable. A 3% edge on a 20% vig market is still losing money.
The Vig Equation
You are not competing against the other side—you are competing against the price.
Your Edge = Your Estimated Probability - Break-Even Probability
If Edge > 0: +EV (bet)
If Edge < 0: -EV (pass)
If Edge = 0: Break-even (pass, vig still costs you)
Use the Vig Calculator
Calculate the vig on any market:
Vig Calculator
Try the interactive calculator for this concept
📝 Exercise
Instructions
Test your understanding of how vig affects your betting.
A market shows Over -120 / Under +100. What is the total implied probability (before removing vig)?
Why do one-way markets (like 'Anytime TD Scorer: Yes +110') have higher vig?
At -110/-110, you need to win 52.4% to break even. If you win exactly 52.4%, what is your ROI?