What Does Devigging Mean?
Devigging is the process of removing the built-in margin (called the vig, vigorish, or juice) from a sportsbook's odds to reveal the true implied probability of each outcome. Every sportsbook inflates its odds so that the implied probabilities of all outcomes sum to more than 100%, and that excess is how the book guarantees itself a profit regardless of the result.
When you devig a line, you're reverse-engineering what the sportsbook actually believes the fair probabilities are — before they added their margin on top. This devigged probability becomes the foundation for calculating whether any bet at any other sportsbook is positive expected value (+EV).
Why Sportsbook Odds Include a Margin
Imagine a perfectly fair coin flip. The true probability of heads is 50%, so fair odds would be +100 (decimal 2.00) on each side. A sportsbook offering +100/+100 would have zero edge and no guaranteed profit — not a viable business model.
Instead, sportsbooks offer something like −110/−110. Let's break down why:
| Side | American Odds | Decimal Odds | Implied Probability |
|---|---|---|---|
| Heads | −110 | 1.909 | 52.38% |
| Tails | −110 | 1.909 | 52.38% |
| Total | 104.76% |
The implied probabilities sum to 104.76% instead of 100%. That extra 4.76% is the vig — the sportsbook's built-in edge. No matter which side wins, the book collected more in total implied probability than 100%, which translates to a mathematical profit over time.
The vig at different sportsbooks varies:
- Pinnacle: ~2–3% on major markets (very low)
- Circa Sports: ~2–4% on most markets
- DraftKings/FanDuel: ~4–6% on main markets, higher on props
- BetMGM/Caesars: ~5–8% on main markets, 10%+ on some props
Why Devigging Matters for +EV Betting
To know whether a bet has positive expected value, you need to compare the sportsbook's offered odds against the true probability of the outcome. But where does the true probability come from?
The best available proxy is the devigged line from a sharp sportsbook. Pinnacle and Circa Sports set their odds using sophisticated models and attract the sharpest bettors in the world, so their lines are considered the most efficient estimate of reality.
The workflow is:
- Take Pinnacle's (or Circa's) odds on a market.
- Devig those odds to extract the fair probability.
- Compare that fair probability against the odds offered at DraftKings, FanDuel, BetMGM, or any other book.
- If a book's odds imply a lower probability than the fair line, you've found a +EV bet.
Without devigging, you can't do step 2, and without step 2, you have no baseline for identifying edges.
Step-by-Step: Three Devigging Methods
Method 1: Multiplicative (Proportional) Method
This is the simplest and most commonly used approach. You divide each side's implied probability by the total overround to scale them back to 100%.
Formula:
Fair Probability A = Implied Probability A / (Implied Probability A + Implied Probability B)
Worked Example: Pinnacle lists an NFL game at −108/−108.
| Step | Calculation |
|---|---|
| Implied Prob (Side A) | 1 / 1.926 = 0.5192 (51.92%) |
| Implied Prob (Side B) | 1 / 1.926 = 0.5192 (51.92%) |
| Total implied | 103.85% |
| Fair Prob (Side A) | 51.92% / 103.85% = 50.0% |
| Fair Prob (Side B) | 51.92% / 103.85% = 50.0% |
As expected for a symmetric line, each side's fair probability is exactly 50%.
Method 2: Power Method (Shin Method Variant)
The power method adjusts probabilities using an exponent rather than a simple proportional scale. The intuition is that the sportsbook doesn't add vig equally to both sides — the favorite tends to absorb slightly more vig because that's where recreational bettors concentrate their money.
Formula:
Find an exponent k such that: (Implied Prob A)^k + (Implied Prob B)^k = 1
Then: Fair Probability A = (Implied Prob A)^k
This requires iterative solving (or a tool). The power method is generally considered more accurate than the multiplicative method, especially for lopsided lines where one side is a heavy favorite.
When to use it: For two-way markets (spreads, totals, moneylines) where the odds are significantly asymmetric — for example, −300/+240.
Method 3: Additive Method
The additive method subtracts an equal share of the overround from each side's implied probability.
Formula:
Overround per side = (Total Implied − 1) / Number of outcomes
Fair Probability A = Implied Probability A − Overround per side
Worked Example: Same −108/−108 line.
| Step | Calculation |
|---|---|
| Total overround | 103.85% − 100% = 3.85% |
| Overround per side | 3.85% / 2 = 1.925% |
| Fair Prob (Side A) | 51.92% − 1.925% = 50.0% |
| Fair Prob (Side B) | 51.92% − 1.925% = 50.0% |
The additive method works well for symmetric or near-symmetric lines but becomes less accurate for heavily skewed markets because it assumes the vig is distributed equally — which it usually isn't.
Which Method Should You Use?
| Method | Best For | Accuracy | Complexity |
|---|---|---|---|
| Multiplicative | Symmetric lines, quick estimates | Good | Low |
| Power | Asymmetric lines, precise EV calculation | Best | Medium |
| Additive | Symmetric lines, simple mental math | Fair | Low |
For serious +EV betting, the power method is the gold standard. For quick back-of-the-napkin calculations, the multiplicative method is fast and reliable enough.
Which Sharp Books to Use as Your Reference
Not all sportsbooks are equal when it comes to devigging. You want to devig the sharpest, most efficient lines available:
- Pinnacle — The industry benchmark for sharp odds. Pinnacle welcomes unlimited sharp action, which means their lines are shaped by the best bettors in the world. Available internationally; not licensed in most US states, but their odds are publicly viewable.
- Circa Sports — The sharpest US-based sportsbook, available in Nevada, Colorado, Iowa, and Kentucky. Circa's limits are among the highest in the industry, attracting professional bettors.
Using a recreational book (like BetMGM or Caesars) as your devigging reference would defeat the purpose — their lines already include larger margins and are less likely to reflect true market probabilities.
Worked Example: Devigging −110/−110
This is the most common line you'll encounter in NFL and NBA spread betting. Here's the full devigging walkthrough:
| Component | Value |
|---|---|
| Side A odds | −110 (decimal 1.909) |
| Side B odds | −110 (decimal 1.909) |
| Implied Prob A | 1 / 1.909 = 52.38% |
| Implied Prob B | 1 / 1.909 = 52.38% |
| Total implied | 104.76% |
| Devigged Fair Prob A (multiplicative) | 52.38% / 104.76% = 50.0% |
| Devigged Fair Prob B (multiplicative) | 52.38% / 104.76% = 50.0% |
Now suppose FanDuel offers Side A at +105 (decimal 2.05). The implied probability at FanDuel is 1/2.05 = 48.78%. Since the fair probability is 50% and FanDuel is offering odds that imply only 48.78%, there's a positive edge:
EV% = (0.50 × 2.05) − 1 = +2.5%
That +2.5% edge was only discoverable because you devigged the sharp line first.
How WagerWiz Handles Devigging Automatically
WagerWiz takes the math out of your hands entirely. The platform:
- Pulls real-time odds from sharp references including Pinnacle-caliber sources
- Applies the power method to devig every market automatically
- Displays the fair probability and fair odds alongside every sportsbook's offered price
- Calculates the EV% for every bet that exceeds your chosen threshold
- Covers all major sports and leagues: NFL, NBA, MLB, NHL, NCAAF, NCAAB, EPL, La Liga, UFC, tennis, and more
Instead of building spreadsheets and manually solving for exponents, you open WagerWiz and see which bets have an edge — with the devigging already done in the background.
FAQ
Do I need to devig every bet I make?
If you're betting for profit rather than entertainment, yes. Devigging is how you establish the fair probability baseline that makes +EV identification possible. Without it, you're guessing whether a bet has an edge. Tools like WagerWiz automate this, so you don't need to do the math manually for every wager.
Is the multiplicative method good enough, or should I always use the power method?
For most bettors, the multiplicative method is a solid starting point and produces results very close to the power method on symmetric or near-symmetric lines. The power method becomes meaningfully more accurate on asymmetric markets (e.g., −250/+210). If you're serious about precision, use the power method or a tool that applies it automatically.
Can I devig odds from any sportsbook?
Technically yes, but the result is only useful if the starting odds are efficient. Devigging BetMGM's line gives you BetMGM's estimate of fair odds — which may be skewed by their recreational customer base. For reliable fair probabilities, always devig from a sharp book like Pinnacle or Circa Sports.
What's a "normal" vig percentage?
On major markets (NFL spreads, NBA totals), sharp books like Pinnacle have ~2–3% vig. Recreational US books like DraftKings and FanDuel typically carry 4–6%. Player props and exotic markets can have vig of 10–20% or even higher, which is why those markets often contain the largest +EV opportunities when a recreational book misprices a line.
How often do devigged fair odds change?
Fair odds shift whenever the sharp line moves — which can be constantly as new information enters the market (injury reports, lineup announcements, sharp betting action). For pre-game markets, the sharpest lines are typically closest to game time. WagerWiz tracks these movements in real time so you always have the current fair odds.
