A book's two prices always imply more than 100% together. Enter both sides and see the fair probability with the vig removed, plus the book's hold.
A sportsbook prices both sides of a market to sum to more than 100% implied probability. That surplus, the vig (or juice), is the book’s built-in edge. Standard -110/-110 pricing implies 52.38% on each side, 104.76% combined: a 4.55% hold. Removing the vig proportionally gives the fair 50.0%/50.0% the market actually believes.
This matters most when comparing your own read on a game to the market’s. Comparing your probability against the RAW implied number (vig included) understates your edge on the favorite side and overstates it on the underdog side. Compare against the fair, de-vigged number instead. See expected value for why that distinction changes the math.
NoPunt’s own model publishes a probability for every game independent of the market, then compares it to the de-vigged price to flag real disagreements. Pro members get the flagged plays; see the Edge for how that works.