Devig calculator
Paste the odds a book or a prediction market is showing. Get back the vig-free fair probability — the number the market is actually implying once you strip out the house margin. No signup, no server; it all runs in your browser.
Fair, vig removed
| Outcome | Your odds | Implied | Fair prob | Fair odds |
|---|
This is the free part.
The devig is the easy 5%. The hard part is watching Polymarket, Kalshi and the books in real time and flagging the deviations that clear the round-trip cost — the +EV scanner NullEdge is building. Want it when it launches? Leave an email. No spam, one launch note.
Devig turns book/market odds into a fair probability by removing the overround (the vig). The multiplicative method scales every implied probability down proportionally; the additive method subtracts the excess equally. Multiplicative is the common default; on longshots the two disagree, which is exactly where naive devig misleads. This tool is a utility, not advice.