Every sportsbook line is inflated. Both sides of a market are priced slightly above their true probability so the book profits regardless of the outcome. Stripping out that inflation — calculating no-vig fair odds — reveals the market’s real assessment of each outcome.
What Are No-Vig Fair Odds?
No-vig (or “de-vigged”) fair odds are what the betting line would look like if the sportsbook charged zero commission. They represent the true probability the market assigns to each outcome.
Standard Line vs. Fair Odds
| Side A | Side B | Total | |
|---|---|---|---|
| Sportsbook line | -150 (60.0%) | +130 (43.5%) | 103.5% |
| No-vig fair odds | -139 (58.0%) | +139 (42.0%) | 100.0% |
The sportsbook line totals 103.5%. The no-vig line totals exactly 100%. That 3.5% difference is the vig.
How to Calculate No-Vig Odds
Step 1: Convert to Implied Probability
Side A at -150: 150 / (150 + 100) = 60.0%
Side B at +130: 100 / (130 + 100) = 43.5%
Total: 103.5%
Step 2: Normalize to 100%
Divide each side’s implied probability by the total:
Side A fair: 60.0% / 103.5% = 58.0%
Side B fair: 43.5% / 103.5% = 42.0%
Total: 100.0%
Step 3: Convert Back to Odds
Side A: 58.0% → -138
Side B: 42.0% → +138
These are the no-vig fair odds.
Why No-Vig Matters
Finding Value
The primary use of no-vig odds is identifying value bets. Here’s the process:
Calculate no-vig fair odds from a sharp sportsbook (like Pinnacle)
Compare to the odds offered at your sportsbook
If your book offers better odds than fair value, the bet is +EV
Example: Sharp no-vig fair odds say Side B is +138. Your sportsbook offers Side B at +155. That’s a +EV bet — you’re getting paid more than the true probability warrants.
Comparing Sportsbooks
Different books have different overrounds. Calculating no-vig odds from each book normalizes the comparison:
| Book | Side A | Side B | Overround |
|---|---|---|---|
| Book 1 | -155 | +135 | 3.9% |
| Book 2 | -145 | +125 | 4.4% |
| Book 3 | -150 | +140 | 2.8% |
Book 3 has the lowest overround — they’re charging the least vig. But the best bet depends on which side you’re betting and which book gives the best individual line.
Estimating True Probability
When sharp sportsbooks with low margins price a market, their no-vig odds are a reliable estimate of the true probability. This is the foundation of many +EV strategies: use sharp books to establish fair value, then find softer books offering better prices.
Sharp Books vs. Soft Books
Not all sportsbook lines are equally informative for de-vigging:
Sharp books (Pinnacle, Circa) have low margins and lines that reflect sharp money. Their no-vig odds are the best proxy for true probability.
Soft books (many US consumer books) have higher margins and lines influenced more by recreational money. Their no-vig odds are less reliable as a probability estimate.
For +EV identification, always de-vig sharp lines first, then compare against the lines at softer books where you’re placing bets.
Limitations
No-vig calculation assumes the vig is equally distributed between both sides. This isn’t always true — some books shade their lines toward the public side, putting more vig on the popular bet. Advanced de-vigging methods (like the power method or Shin method) account for this asymmetry, but the basic proportional method works well enough for most bettors.
Key Takeaways
No-vig fair odds remove the sportsbook’s margin to reveal true market probability
Calculate by normalizing implied probabilities to sum to 100%
Use sharp book no-vig odds as your baseline for fair value
Compare fair value to the odds at your sportsbook to find +EV bets
