Every betting line is telling you two things at once: what the book thinks will happen, and how much it charges you to have an opinion. Those are tangled together, and if you can't separate them you'll misjudge almost every bet you look at. The tool that pulls them apart is the no-vig (or 'fair odds') calculation. Learn it once and you'll never look at a price the same way again — you'll see straight through the marketing number to the real probability underneath.
What the vig actually is
The vig — also called juice or the hold — is the sportsbook's commission. It's the reason a coin-flip market isn't priced at +100 / +100 (a fair 50/50) but at -110 / -110. That extra ten cents on each side is the book's cut. You can see it clearly by converting the odds to implied probability. American odds of -110 imply a 52.38% chance. Both sides at -110 sum to 104.76%, not 100%. That extra 4.76% is the vig, sometimes called the 'overround.'
A market whose implied probabilities sum to more than 100% is the book's edge in numeric form. The higher that sum climbs above 100%, the more juice is baked in and the worse your price. Alternate lines, same-game parlays, and obscure props often carry a much fatter overround than a mainstream point spread — which is exactly why devigging matters most in the corners of the board where books think you won't check.
How to remove the vig from a two-way market
The standard method is the 'multiplicative' de-vig, and it's refreshingly simple. Convert each side to its raw implied probability, add them up, then divide each side by that total. Dividing by the sum rescales both numbers so they add to exactly 100% — the vig is gone, and what remains is the book's true (fair) estimate for each outcome. Those fair probabilities convert back into fair odds, which are the price you'd need for a break-even, zero-margin bet.
- 1Convert each side of the market to implied probability.
- 2Add the two implied probabilities together (this sum will exceed 100%).
- 3Divide each side's probability by that sum to rescale to 100%.
- 4Convert the resulting fair probabilities back into fair (no-vig) odds.
De-vigging a symmetric -110 / -110 line
- Posted line
- Over 44.5 -110 / Under 44.5 -110
- Over implied prob
- 110 / (110 + 100) = 52.38%
- Under implied prob
- 52.38%
- Sum (overround)
- 52.38% + 52.38% = 104.76%
- Fair Over
- 52.38% / 104.76% = 50.0%
- Fair Under
- 50.0%
- No-vig odds
- +100 / +100 (a true coin flip)
A symmetric line devigs to a clean 50/50. All the -110 was doing was hiding the 4.76% hold.
The symmetric case is the 'hello world' of devigging. The real payoff comes with a lopsided line, where the two sides aren't priced the same and your intuition can't just eyeball the fair number.
De-vigging a lopsided moneyline
- Posted line
- Favorite -230 / Underdog +190
- Favorite implied prob
- 230 / (230 + 100) = 69.70%
- Underdog implied prob
- 100 / (190 + 100) = 34.48%
- Sum (overround)
- 69.70% + 34.48% = 104.18%
- Fair favorite
- 69.70% / 104.18% = 66.90%
- Fair underdog
- 34.48% / 104.18% = 33.10%
- Fair odds
- ≈ -202 favorite / ≈ +202 underdog
The book's true read on the favorite is ~66.9%, not the 69.7% the raw -230 implies. If you can find that dog at +210 elsewhere, you're getting a better price than fair.
Multi-way markets: same idea, more legs
Plenty of markets have more than two outcomes: a 3-way soccer line (home win, draw, away win), 'first player to score,' round-betting on a UFC fight, or an outright to win a golf tournament. The math is identical — you just sum every outcome's implied probability and divide each one by that grand total. A 3-way soccer market might sum to 106% or 107% instead of ~105%, because more outcomes usually means more places to hide juice.
A caveat worth knowing
The simple 'divide by the sum' method assumes the vig is spread proportionally across every outcome. In heavy-favorite markets that slightly overstates the favorite's fair chance, because books tend to load more juice onto longshots. Advanced bettors use weighted methods (like the Shin or logarithmic models) to correct for this. For most two-way spreads and totals, the proportional method is more than accurate enough to make good decisions.
Turning no-vig lines into +EV bets
Here's where devigging earns its keep. A single book's no-vig line is that book's honest opinion of the true probability. But no book is the sharpest on every market. The play is to build a fair line from a sharp, low-hold source (or a consensus of books), then shop for a book offering a better number than that fair line. When the price you can actually bet is longer than fair value, the bet is +EV — positive expected value — over the long run.
- Devig a sharp market to get the fair probability of the side you like.
- Find the best available price for that side across the books you can bet.
- Compare the best price's implied probability to your fair probability.
- If the best price implies a LOWER probability than fair, you're getting a longer number than the outcome deserves — that's your edge.
Spotting the edge
- Fair (no-vig) probability of the Under
- 50.0%
- Best available price on the Under
- +105 at another book
- +105 implied probability
- 100 / (105 + 100) = 48.78%
- Edge
- 50.0% fair − 48.78% priced = +1.22% EV
- Read
- You're being paid as if the Under is 48.78% when fair value says ~50%.
A ~1-2% edge is small per bet but meaningful across hundreds of wagers. This is how disciplined bettors grind, not how anyone gets rich on one ticket.
Where devigging fits in a real workflow
No-vig math is a benchmark, not a crystal ball. It tells you what a market currently believes and how much you're overpaying, but it can't tell you whether the market is wrong. That's where an independent model comes in: Statly's Edge engine builds its own projection for a player or game from historical performance, matchup, and situational factors, then compares that projection to the no-vig line. When our number and the fair line disagree meaningfully, that's a candidate bet. Devigging keeps you honest about the price; the model gives you an opinion about the outcome.
The honest bottom line
De-vigging improves how you read a line and where you place your money — it does not make any single bet a sure thing. Odds are probabilities, not promises, and variance means good bets lose all the time. Bet only what you can afford to lose, treat this as information and analytics rather than financial advice, and step away if it stops being fun. 21+ where legal.
Master the two-way de-vig first, get comfortable reading the overround, and the multi-way markets and +EV hunting fall into place. Once you can strip the juice off any line in your head, you're no longer betting the number the book wants you to see — you're betting the number underneath it.