Gambling Online 101
intermediate
9 min readDevigging: Removing the Vig
How to strip the sportsbook margin from any line to reveal the true implied probability.
BonusBell Team
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 trueimplied 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. The important caveat is that a no-vig number is a model estimate of fair probability, not a revealed truth from the market gods.
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:
Vig in Action
-110 / -110 line: Each side = 110/(110+100) = 52.38%=Total implied probability: 52.38% + 52.38% = 104.76%
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 usually means more efficient pricing. Price-discovery books often run tighter margins than recreational apps.
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, especially when the book shades favorites and longshots unevenly.
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."
Multiplicative Devig
Fair Prob = Raw Implied Prob / Total Overround=-150 / +130 line: Favorite = 60% / 1.0369 = 57.87% | Underdog = 43.48% / 1.0369 = 41.93%
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
Multiplicative is a shortcut, not a finish line. It assumes the book applies its margin proportionally to both sides. That is useful for fast mental math, but real books can shade favorites and longshots differently.
2. Power Method (Practical Default for Many 2-Way Markets)
The power method finds an exponent ksuch 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. In published comparisons, it performs well as a two-outcome no-vig approximation.
Power Method Concept
Find k where: (1/odds_A^k) + (1/odds_B^k) = 1=For -150 / +130: k ≈ 1.033 → Favorite = 57.58%, Underdog = 42.42%
The power method shifts slightly more vig onto the underdog side. That often lines up better with how real books shade prices than a straight proportional haircut.
Strategy Insight
Many no-vig tools use the power method as a practical default for 2-way markets. Use it for NFL/NBA/MLB/NHL spreads, totals, and standard moneylines when you want something more robust than quick proportional math. BonusBell's No-Vig Calculator implements this method by default.
3. Shin Method (Classic Theory-Driven Approach)
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 margin asymmetrically rather than just dividing it evenly:
Shin Method Application
3-way soccer: Home -125 (55.56%), Draw +250 (28.57%), Away +300 (25.00%)=Overround = 109.13%. Shin devig: Home 51.2%, Draw 25.9%, Away 22.9%
The Shin framework is especially helpful when you want a theory-based way to think about favorite-longshot distortion in multi-outcome books.
Analysts often reach for Shin-style adjustments in markets with 3+ outcomes or visible favorite-longshot skew:
- 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 | Useful For | Tradeoff | Complexity |
|---|---|---|---|
| Multiplicative | Fast sanity checks | Quick but blunt | Simple division |
| Power | 2-way markets (spread, total, ML) | Practical and flexible | Requires solver |
| Shin | 3+ way markets or skewed books | More theory-heavy | Iterative algorithm |
Model choice changes the fair price. Use devigging as disciplined estimation, not false precision.
Try It: Remove the Vig
Enter any 2-way line to see the no-vig fair odds and true implied probability:
Model It: Two-Way No-Vig Lab
Enter both sides of the same two-way market. The lab strips out the bookmaker margin, then shows how a quick multiplicative estimate compares with a power-method approximation that many no-vig tools use for two-outcome prices.
Market view
52.4% + 52.4%
-110 / -110 implies a 4.76% overround before you even decide whether there is value.
Quick estimate
Multiplicative fair lines
Side A-100
Side B-100
Practical default
Power-method fair lines
Side A-100
Side B-100
Model gap
0.00 pts
Small differences are normal. No-vig numbers are model outputs, not revealed truth.
MethodSide ASide B
Raw implied52.38%52.38%
Multiplicative50.00%50.00%
Power50.00%50.00%
Use this on the same two sides of the same market only. If you want a quick fair line from a sharp book, this is the right workflow. If you want certainty, it does not exist.
Good to Know
No-vig numbers are model outputs. If two thoughtful methods disagree slightly, that does not mean one of them is broken. It means you are estimating an unobservable fair price from a vigged market, not extracting a hidden answer key.
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.
Devig-Based +EV Example
Pinnacle: -148/+132 → Power devig: Favorite 58.7% fair | DraftKings: Favorite at -140 (58.33% implied)=Edge = 58.7% − 58.33% = +0.37% (marginal, probably a pass)
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
A common mistake is devigging a soft book's line and treating that as the fair probability. Don't do this. Soft books are less efficient—their vigged probabilities may not bracket the true probability. Always devig from a sharp source like Pinnacle.
Good to Know
Devigging is built into BonusBell's tools. The EV Finder automatically devigs sharp consensus lines and compares them to soft book prices. The Universal Bet Calculator shows hold percentages and devigged probabilities for any market you enter.
Common Mistakes
- Using the wrong method. Multiplicative on 3-way soccer markets will give you only a rough estimate. Use a method built for asymmetry when the market has more than two meaningful 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.
Related Reading
- Understanding Odds— convert any price into implied probability before you try to remove the vig from it
- Expected Value— what the no-vig fair line means once you compare it to the price you can actually bet
- Closing Line Value— the long-run scoreboard for whether your fair-price workflow is beating the market
Sources & References
- Overround is simply the sum of all implied probabilities minus 100%, so the basic vig math on two-way books is independently verifiable from the posted prices.
- Clarke, Kovalchik, and Ingram compare common overround-adjustment methods and report strong practical performance for the power method across several sports datasets. (Adjusting Bookmaker’s Odds to Allow for Overround)
- Hyun Song Shin (1991), Optimal Betting Odds Against Insider Traders. Shin’s classic framework models bookmaker margin in the presence of insider trading and remains one of the central references for asymmetric no-vig estimation.
- A no-vig line is still an estimate of fair probability, which is why serious bettors compare methods, compare books, and treat tiny “edges” cautiously.
Mathematical claims are independently verifiable. BonusBell platform analysis reflects our tracked platform directory and dated evidence checks 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
- 3Power is a strong practical default for many 2-way markets, but it is still a model
- 4Shin-style adjustments are most useful when favorite-longshot skew or multi-outcome books matter
- 5Always devig from sharp book lines (Pinnacle) — never treat a soft book's devigged probability as "true"