Devig Explained: 3 Methods to Strip the Bookmaker's Margin

What is devigging?

Every sportsbook adds a margin to their odds. This margin is called the vig (short for vigorish), juice, or overround. It is how bookmakers guarantee a profit over time, regardless of the outcome. When you look at a set of odds, the implied probabilities always add up to more than 100%. That extra percentage is the bookmaker's cut.

For example, a fair coin flip has a true probability of 50% for each side. A bookmaker might offer 1.91 on heads and 1.91 on tails. If you convert those odds to implied probabilities, each side is 52.36%. That adds up to 104.72%, not 100%. The extra 4.72% is the margin.

Devigging strips that extra margin away. After you devig, the same coin flip goes back to 50%/50%. For an NFL spread or a soccer match, the true probability is not obvious at all. That is why devigging matters.

The true probability tells you what the market actually thinks will happen. Once you know the true probability, you can compare it to prices at other bookmakers. If another book offers odds that imply a lower probability than the true probability, you have found a positive expected value (+EV) bet.

Why the vig exists

Bookmakers are businesses. They need to make money on every market they offer, no matter who wins. The vig is their primary revenue tool. It works like a transaction fee built into the odds themselves.

Think of it this way. In a perfectly balanced two-way market, the bookmaker takes equal action on both sides. With a 4.5% margin, they collect more money from losing bets than they pay out on winning bets. The margin is the gap between what bettors pay and what bettors receive.

Sharp bookmakers like Pinnacle operate on thin margins because they attract high-volume, knowledgeable bettors. Pinnacle charges around 2% on liquid markets like NFL spreads, compared to the 5-8% industry average at recreational bookmakers. Soft bookmakers charge more because their customers are less price-sensitive.

Typical margin at Pinnacle on major two-way markets: 2-3%. Typical margin at soft books like bet365, DraftKings, FanDuel: 5-8%. Margin on player props, parlays, and exotic bets: 15-40%.

These differences in margin are exactly why devigging is useful. A 5% margin at a soft book means the odds are 5% worse than fair. Devigging lets you extract the true probability hidden inside those odds.

How to devig: step by step

There are three main methods for devigging odds. Each one handles the margin differently. Here is a walkthrough using the same example for all three: an NFL spread with Pinnacle odds of 1.93 / 1.93.

Step 1: Convert the decimal odds to implied probabilities. Side A: 1/1.93 = 51.81%. Side B: 1/1.93 = 51.81%. Total: 103.63%. The overround (margin) is 3.63%.

Multiplicative method (basic)

This is the simplest approach. Divide each implied probability by the total to scale everything back to 100%.

Formula: True probability = Implied probability / Sum of all implied probabilities

Worked example (NFL spread 1.93 / 1.93): Raw implied 51.81% each -> Divide by total 1.0363 -> True probability 50.00% each -> No-vig odds 2.00 each.

The multiplicative method assumes the margin is spread equally across all outcomes. This works well when both sides have similar odds (like NFL spreads). It breaks down when there is a heavy favorite and a big longshot.

Power method (odds-based)

The power method adjusts for uneven margin distribution. Bookmakers tend to load more margin onto the longshot side. Using a lopsided example with odds of 1.25 / 4.20:

Formula: Find the exponent k such that (1/odds_A)^k + (1/odds_B)^k = 1. Then, true probability for each side = (1/odds)^k.

Comparison for 1.25 / 4.20 market: Multiplicative devig gives 77.07% / 22.93%. Power method gives 78.12% / 21.88%. The power method assigns a higher true probability to the favorite and a lower probability to the underdog, which matches real market behavior.

Shin method

The Shin method is named after economist Hyun Song Shin, whose 1991 paper showed that bookmaker odds diverge systematically from true probabilities due to the presence of informed bettors. It models the bookmaker's margin as protection against bettors who have insider knowledge.

The Shin model distributes more margin onto outcomes where insider information would be most valuable. In practice, favorites carry slightly less margin than longshots, similar to the power method, but with a different theoretical basis. Most bettors use calculators or spreadsheets for this method.

Devig methods compared

Multiplicative: Simple division, assumes equal margin across all outcomes. Best for even-money two-way markets. Can be done with a calculator.

Power Method: Requires a solver, assumes more margin on longshots. Best for lopsided two-way markets. Requires a spreadsheet or tool.

Shin Method: Most complex, margin modelled from insider risk. Best for three-way markets and soccer. Requires a dedicated tool.

In practice, most successful +EV bettors use the multiplicative method for NFL and NBA markets and the power method when dealing with moneylines on heavy favorites.

Practical examples

Example 1: NFL spread

Pinnacle offers Chiefs -3.5 at 1.95 and Bills +3.5 at 1.93. After devigging: Chiefs -3.5 implied 51.28% -> true 49.69% -> no-vig odds 2.013. Bills +3.5 implied 51.81% -> true 50.21% -> no-vig odds 1.992. If a soft book offers Bills +3.5 at 2.05, the implied is 48.78%, below the devigged fair of 50.21%. That is a +EV bet.

Example 2: Soccer match winner (three-way)

Pinnacle offers Liverpool 1.72, Draw 4.00, Arsenal 4.80. After multiplicative devigging: Liverpool 56.43% -> no-vig 1.772. Draw 24.27% -> no-vig 4.120. Arsenal 20.22% -> no-vig 4.946. Total implied was 103.97%, devigged to 100%.

Example 3: NBA total (over/under)

Pinnacle offers Over 218.5 at 1.91 and Under 218.5 at 1.97. After devigging: Over 50.80% -> no-vig 1.969. Under 49.25% -> no-vig 2.031. If DraftKings offers the Over at 1.98, that implies 50.51%. The edge is about 0.3% - thin but meaningful over high volume.

How to use devigged odds

Devigging is the foundation of positive expected value (+EV) betting. Here is the practical workflow most sharp bettors follow.

• Step 1: Get the sharp line. Use Pinnacle's odds as your starting point. They have the lowest margins and most efficient closing lines.
• Step 2: Devig the line. Remove Pinnacle's margin using the multiplicative or power method to get the estimated true probability.
• Step 3: Convert to fair odds. Turn the devigged probability back into decimal odds. This is your benchmark: the price at zero expected value.
• Step 4: Compare to soft books. If their odds are higher than your fair odds, you have found a +EV bet.
• Step 5: Size your bet. Use Kelly criterion or a fixed percentage of your bankroll. The bigger the edge, the more you can bet.

Connection to closing line value (CLV)

Devigging and closing line value (CLV) are closely connected. CLV measures whether you beat the closing line. If you devig those closing odds, you get the market's final estimate of the true probability.

Bettors who consistently find +EV edges through devigging tend to achieve positive CLV on 55-60% of their bets. That translates to an expected ROI of 2-5% over thousands of wagers.

Devigging for matched betting

Even if you focus on matched betting, understanding devigged odds helps you find better qualifying bets. Choosing a market where the soft book's margin is lowest reduces your qualifying loss. Over hundreds of free bet conversions, this saves a meaningful amount of money.

When devig doesn't work well

Devigging is powerful, but it has real limitations. Knowing when not to trust it is just as important as knowing how to use it.

Low-liquidity markets

Devigging works best on markets where large amounts of money have shaped the odds. NFL spreads, NBA totals, and major soccer leagues attract billions in handle. Low-liquidity markets like minor league baseball, lower-division European soccer, or niche esports may have odds set by a single bookmaker's model rather than market forces.

Player props and exotic bets

Player props carry huge margins, often 15-30% or more. Even after removing the margin, the underlying odds may still be wrong. Props are often set by automated models with limited data. A sharp line on an NFL spread exists; a sharp line on a player prop usually does not.

Three-way markets

Soccer matches and any market with three or more outcomes are harder to devig accurately. The margin is distributed unevenly, and different methods produce noticeably different results. Use the Shin method when possible, and be cautious with any edge below 3%.

Stale or early lines

Opening lines are less efficient than closing lines. If you devig an opening line posted 4 days before an NFL game, that devigged probability will change as new information enters the market. Devigging is most useful on lines that have been shaped by sharp money, usually close to the event start time.

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