How to Remove the Vig: Multiplicative, Additive, Power, and Worst-Case Methods
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Key takeaways
- Devigging turns a sharp book’s prices into fair probabilities by removing its margin.
- On close markets (near −110 / −110) every method gives almost the same answer.
- On lopsided markets the methods disagree, and that disagreement can decide whether an underdog bet is +EV.
- Because books tend to load more margin onto longshots, power or worst-case methods are safer for underdogs.
Every sportsbook price includes the bookmaker’s margin, also called the vig or juice. To judge whether a bet is worth taking, you need to strip that margin out and see the probability the market actually believes. That process is called devigging.
This guide covers the four common methods, shows where they agree and disagree, and explains which to use when.
Why devig at all?
Say a sharp book prices a game at −110 / −110. Each side implies 52.38%, adding up to 104.76%. Neither side really has a 52.38% chance; the book has inflated both. Removing the extra 4.76% shows the fair split, 50% / 50%.
The fair probability is what you compare against other books’ prices. If fair is 50% and another book offers +110 (47.62% implied), that bet is +EV. See positive EV betting explained.
The four methods
In each method, qᵢ is the implied probability of outcome i (1 ÷ decimal odds), and n is the number of outcomes.
1. Multiplicative (proportional)
Scale every implied probability down by the same factor. It’s simple, the most widely used, and works well on evenly matched markets. It assumes the book took margin proportionally from every outcome.
2. Additive
Subtract the same amount from every outcome. It removes relatively more from longshots, and on very lopsided markets it can produce negative probabilities, which is a sign it doesn’t fit.
3. Power
Raise each implied probability to a power slightly above 1. Smaller probabilities shrink proportionally more, so longshots absorb more of the margin. You solve for k numerically, which is what the calculator does.
4. Worst case
Run the other methods and, for each outcome, take the lowest fair probability. If a bet is +EV even under its least favorable estimate, you can be confident the edge isn’t an artifact of the method.
Run the numbers: What are the true odds once the bookmaker margin is removed? Open the No-Vig Fair Odds Calculator
Close markets: the methods agree
A sharp book posts −115 / +105.
| Method | Favorite | Underdog |
|---|---|---|
| Implied | 53.49% | 48.78% |
| Multiplicative | 52.30% | 47.70% |
| Additive | 52.35% | 47.65% |
| Power | 52.38% | 47.62% |
The differences are under a tenth of a percentage point. For evenly matched markets, use multiplicative and move on.
Lopsided markets: the methods diverge
Now a sharp book posts a favorite at −300 and the underdog at +240. Implied probabilities are 75.00% and 29.41%, a 4.41% overround.
| Method | Favorite fair | Underdog fair |
|---|---|---|
| Multiplicative | 71.83% (−255) | 28.17% (+255) |
| Additive | 72.79% (−268) | 27.21% (+268) |
| Power | 73.31% (−275) | 26.69% (+275) |
Now suppose a US book offers the underdog at +265 (3.65):
The same price is +EV under one method and −EV under another. This is the case where method choice matters.
Get +EV bets flagged against sharp prices
ProfitDuel's EV Matcher and Odds Screener compare US sportsbook prices with the sharpest books in the world and surface bets that beat the fair line.
Start the $1 ProfitDuel trialAffiliate link. The $1, 3-day trial applies to ProfitDuel's Starter plan as listed in September 2026. 21+ and in states where online sports betting is legal.Which method should you use?
The favorite-longshot bias. Across many sports and many decades, longshots have tended to win less often than their odds suggest, and favorites slightly more. Bookmakers price this in, effectively placing more of their margin on longshots. Methods that do the same, like power and Shin, tend to fit real outcomes better in lopsided markets.
Practical guidance:
- Near-even markets: multiplicative. All methods agree anyway.
- Betting underdogs in lopsided markets: power, or worst case to be safe.
- Betting favorites in lopsided markets: multiplicative is the conservative choice, since it gives favorites the lowest fair probability.
- Unsure: worst case. You’ll skip some marginal bets, but the ones you take will hold up.
Common devigging mistakes
- Mixing books. Devig one book’s market at a time. Combining the best price from each side at different books gives you an arbitrage check, not a fair line.
- Devigging one-sided markets. If a prop only shows an over, you can’t measure the margin reliably.
- Trusting thin markets. A devigged price from a low-limit market is only as good as the money behind it. See when the sharp line is less reliable in our Pinnacle guide.
- Ignoring stale prices. Devig the sharp line as it stands when you bet, not an hour-old snapshot.
The no-vig calculator runs all four methods side by side, and the expected value calculator lets you pick a method and see the EV of a specific bet.
Frequently asked questions
What is the most accurate devig method?
There’s no single answer. Multiplicative is the most common default. Many analysts find that methods which assign more margin to longshots, like power or Shin, fit real results better in lopsided markets. Worst case is a cautious choice when you’re unsure.
Can I devig a market with more than two outcomes?
Yes. All four methods work for three-way markets like soccer 1X2, and for futures with many outcomes, though futures margins are large and less reliable.
What is the Shin method?
Shin’s method, from economist Hyun Song Shin, models the margin as the bookmaker protecting itself against bettors with inside information. It tends to give results similar to the power method, assigning more margin to longshots.
Get +EV bets flagged against sharp prices
ProfitDuel's EV Matcher and Odds Screener compare US sportsbook prices with the sharpest books in the world and surface bets that beat the fair line.
Start the $1 ProfitDuel trialAffiliate link. The $1, 3-day trial applies to ProfitDuel's Starter plan as listed in September 2026. 21+ and in states where online sports betting is legal.