Fair Odds & De-Vigging Explained
How to strip the vig out of a market to reveal the true, fair probability - the reference every value bet is measured against.
Fair odds (or no-vig odds) are what a price would be if the sportsbook took no margin. Because real odds always include the vig, de-vigging is how you uncover the market's honest estimate of an outcome's probability - the number you compare every bet against.
Why raw odds mislead you
If a market is priced −110 / −110, both sides imply 52.4%, totaling 104.8%. Neither number is the true probability - they're inflated by the vig. To find the fair probabilities, you scale them so they add back to 100%.
The simplest method: proportional (multiplicative) de-vig
- Convert each side to implied probability.
- Add them up (you'll get more than 100%).
- Divide each side's implied probability by that total.
Example: Side A −130 (56.5%) and Side B +110 (47.6%) sum to 104.1%. Fair A = 56.5 ÷ 104.1 = 54.3%; Fair B = 47.6 ÷ 104.1 = 45.7%. Those add to 100% - the vig is gone.
Using the fair line
Once you have fair probabilities from the No-Vig Fair Odds Calculator, you can convert them back to "fair odds" and compare them to the price you are betting. Whenever your price pays *more* than the no-vig fair odds on that side, the wager is mathematically +EV.
There's more than one method
Proportional de-vig is the most common, but additive, power, and worst-case methods exist and handle favorites/longshots differently. For most bettors, proportional de-vig is accurate enough; the nuances are covered in De-Vig Methods.
Put theory into practice with SharpWire quantitative tools
Verify situational angles, strip bookmaker vig to find true fair-value probabilities, and uncover mathematical edges on the live board.
