Devig Calculator
Both sides of a two-way market in — the book’s margin stripped, fair probabilities and fair odds out.
additive method: over 50.0% / under 50.0%
The gap between each fair tick and its market tick is the edge you keep by shopping — the multiplicative split is what our engine prices with; the additive line is shown only for comparison.
Worked example
A strikeout prop is priced −200 over / +170 under. Implied: 66.7% and 37.0%, a total of 103.7%. Multiplicative devig: over fair = 66.7 / 103.7 = 64.3%, under fair = 35.7%. The fair prices are −180 and +180 — so if another book hangs the under at +190, that’s a +EV side against this market’s own numbers.
FAQ
What does it mean to remove the vig?
Both sides of a market carry implied probabilities that sum to more than 100% — the excess is the book’s margin. Removing the vig rescales the two implied probabilities so they sum to exactly 100%, leaving an estimate of the true chance of each outcome: the fair probability.
Why use the multiplicative method?
The multiplicative (proportional) method divides each implied probability by the total, shrinking both sides in proportion to their size. It’s the most common convention among sharp books and it’s what our engine uses to price every prop on the board. The additive method — splitting the overround evenly — is shown only as a comparison; on lopsided markets the two can differ by a point or more.
What are fair odds?
Fair odds are the price with no margin — the American odds that correspond exactly to the fair probability. If a side devigs to 55%, its fair price is −122; any book offering a better number than −122 on that side is offering +EV relative to this market.
Can I devig a market when one side isn’t priced?
No — and neither do we. A one-sided market has no overround to distribute, so any "fair" number derived from it would be invented. This calculator requires both sides, matching how our engine treats one-sided books: never devigged.
Which book should I devig?
The sharpest one you can see. Pinnacle-style market-makers with high limits and low margins produce the best fair estimates. Devigging a soft recreational book just reproduces that book’s biases.
The morning board, in your inbox
Top +EV rows, biggest line movers, and hot streaks — one email before first pitch. No spam, unsubscribe anytime.