Devigging: Removing the Vig
How to strip the sportsbook margin from any line to reveal the true implied probability.
Every sportsbook line includes a built-in margin—the vig (or juice). A -110/-110 line doesn't imply two 50/50 outcomes; it implies 52.38% + 52.38% = 104.76%. That extra 4.76% is the sportsbook's profit margin. To find the true implied probability of any outcome, you need to remove the vig. This process is called "devigging" and it's the foundation of value betting, +EV analysis, and fair line estimation.
Why Every Line Has Vig
Sportsbooks are businesses. They need a margin to cover operations and generate profit. The vig is embedded in every line they offer:
The 4.76% overround is the sportsbook's margin. In a perfectly balanced market, they keep this ~4.76% regardless of the outcome.
The vig varies by market and sportsbook:
Typical Vig by Market
| Market | Typical Line | Overround | Effective Vig |
|---|---|---|---|
| NFL Spread | -110 / -110 | 104.76% | ~4.76% |
| NFL Moneyline | -180 / +155 | 105.2% | ~5.2% |
| NBA Total | -108 / -112 | 104.6% | ~4.6% |
| Player Props | -120 / -110 | 106.7% | ~6.7% |
| Pinnacle NFL | -104 / -104 | 102.0% | ~2.0% |
Lower vig means more efficient pricing. Sharp books have 2-3% vig; soft books run 4-7%.
The Three Devigging Methods
There are three standard approaches to removing the vig, each with different assumptions about how books distribute their margin across outcomes. The choice matters—different methods can produce meaningfully different fair probabilities.
1. Multiplicative Method (Simplest)
The multiplicative method divides each implied probability by the total overround. It assumes the vig is distributed proportionally—each side is equally "inflated."
Raw implied: Favorite 60.00%, Underdog 43.48% (overround = 103.48%). After devigging, the no-vig line for the favorite is approximately -137.4 and the underdog is approximately +138.5.
Warning
2. Power Method (Best for 2-Way Markets)
The power method finds an exponent k such that when you raise each side's decimal odds to the power k, the resulting implied probabilities sum to exactly 100%. It adjusts for the fact that favorites are typically more accurately priced than underdogs.
The power method shifts slightly more vig onto the underdog side, reflecting that favorites are priced more accurately in practice. This is generally the most accurate method for 2-way markets (spreads, totals, moneylines).
Strategy Insight
3. Shin Method (Best for 3+ Outcomes)
The Shin method, developed by economist Hyun Song Shin, models the vig as a function of insider trading—the idea that some bettors have private information. It distributes more vig onto favorites (where insiders are more likely to bet) and less onto longshots:
Notice how the favorite (Home) loses the most vig while the longshot (Away) loses the least. This reflects the economic reality that insiders are more likely to bet on outcomes they know will happen (usually favorites in match-fixing scenarios).
The Shin method shines in markets with 3+ outcomes:
- Soccer moneylines (Home/Draw/Away)
- Futures markets (conference winner, MVP, etc.)
- Multi-way props (exact score, first goalscorer)
- Horse racing win pools
When to Use Each Method
Devigging Method Selection
| Method | Best For | Accuracy | Complexity |
|---|---|---|---|
| Multiplicative | Quick estimates, low-stakes analysis | Adequate | Simple division |
| Power | 2-way markets (spread, total, ML) | High | Requires solver |
| Shin | 3+ way markets (soccer, futures) | Highest | Iterative algorithm |
Use Power for spreads/totals, Shin for soccer and futures, Multiplicative for quick math
Try It: Remove the Vig
Enter any 2-way line to see the no-vig fair odds and true implied probability:
| Method | Side 1 | Side 2 |
|---|---|---|
| Multiplicative | 50.0% | 50.0% |
| Power (Best) | 50.0% | 50.0% |
Power method is the most accurate for 2-way markets. The vig is removed by finding the exponent that normalizes probabilities to 100%.
Why Devigging Matters for +EV Betting
Devigging is the starting point for every +EV analysis. Here's the workflow:
- Find the sharp consensus. Look at Pinnacle's line on the market.
- Devig the sharp line. Use the power method to find Pinnacle's implied fair probability.
- Compare to soft book odds. If a soft book's implied probability is lower than the devigged fair probability, you have +EV.
- Size your bet. Use the Kelly Calculator to determine optimal bet size based on the edge.
Now imagine DraftKings has it at -130 (56.52% implied). Edge = 58.7% − 56.52% = +2.18%. That's a clear +EV bet worth taking.
Strategy Insight
Good to Know
Common Mistakes
- Using the wrong method. Multiplicative on 3-way soccer markets will give you inaccurate fair odds. Use Shin for 3+ outcomes.
- Devigging soft book lines. The fair probability should come from sharp sources, not the book you're betting at.
- Ignoring the vig entirely. Comparing raw implied probabilities across books without removing vig leads to false value signals.
- Over-trusting small differences. A 0.5% edge after devigging is within the margin of error. Look for 1%+ edges for confidence.
Sources & References
- Shin, H.S. (1991), Optimal Betting Odds Against Insider Traders, The Economic Journal. Developed the Shin method for removing bookmaker margins, modeling the overround as a function of insider trading probability. The method distributes vig inversely to outcome probability, producing more accurate fair odds for multi-outcome markets.
- Power method devigging: iteratively finds exponent k such that sum of (1/odds^k) = 1. Produces accurate 2-way fair probabilities by adjusting for the empirical finding that favorites carry less vig per unit of implied probability. Widely used by professional odds services and betting syndicates.
- Overround (vig) ranges across sportsbook types: sharp books (Pinnacle, Circa) typically operate at 2-3% overround on main markets; recreational-focused US books operate at 4-7%. Data from BonusBell analysis of 220+ tracked platforms.
- Multiplicative devigging as a biased but computationally simple method: dividing each implied probability by total overround assumes proportional vig distribution, which empirical studies show is not reflective of how bookmakers actually construct their margins.
Mathematical claims are independently verifiable. BonusBell platform analysis reflects data from 220+ tracked platforms as of March 2026.
Key Takeaways
- 1Every sportsbook line includes vig (juice) — the overround above 100% is the book's margin
- 2Multiplicative devigging is simple but biased; use it only for quick estimates
- 3The Power method is best for 2-way markets (spreads, totals, moneylines) and is the industry standard
- 4The Shin method is best for 3+ outcome markets (soccer, futures, horse racing)
- 5Always devig from sharp book lines (Pinnacle) — never treat a soft book's devigged probability as "true"