CobiaHow the devig calculator works
Every two-way market has two prices, and if you convert both to implied probabilities and add them up, they'll total more than 100%. That extra slice is the vig — the house's built-in margin. Devigging removes it so you can see the market's true fair-value estimate.
Worked example
Take a market priced -120 / +100. Side A at -120 implies 120/220 ≈ 54.5%; Side B at +100 implies 100/200 = 50%. They sum to 104.5% — so the book is charging a 4.5-point overround. Devig: fair A = 54.5 ÷ 104.5 ≈ 52.2%, fair B = 50 ÷ 104.5 ≈ 47.8%. Those two now add to exactly 100.
Why two prices sum to more than 100%
A fair coin is 50/50 — both sides sum to 100%. A sportsbook can't make money offering fair prices, so it shades both sides a little worse. The gap above 100% is guaranteed profit if the book balances its action. On a heavily-juiced market the two sides might sum to 108% or more; on a sharp, low-margin market they'll sit just above 100%.
Why the no-vig line is the fair-value benchmark
Once you devig, you have the market's honest estimate of each side's probability with the house cut removed. That no-vig number is the benchmark: if you can find the same outcome priced better than its fair no-vig probability somewhere else, that gap is your edge. It's the single most useful number for line-shopping and for spotting +EV bets.