No-vig odds (fair odds, devigged odds)
A book's prices with the margin removed, so the implied probabilities sum to exactly 100% — the book's actual estimate of the outcome.
The simplest devig divides each implied probability by their sum: −110 / −110 becomes 50% / 50%. More careful methods (power, Shin) account for favorite–longshot bias. Sharp bettors devig a low-margin book to estimate true probabilities, then shop softer books for prices above that estimate.
No-vig odds are not what an arbitrageur needs — an arb is about the prices you can actually get — but they explain why the same game carries different prices at different books: each book's fair estimate differs, and each adds its own margin on top.
Measured on ArbMonster: No-vig calculator
Related terms: Vig · Implied probability · Hold