No-vig calculator
Enter both sides of a two-way sportsbook line. The calculator removes the bookmaker’s margin and shows the fair probability for each side, which you can compare with a Kalshi or Polymarket price in cents.
How it works
A sportsbook prices both sides so their implied probabilities add up to more than 100%. The extra is the vig, or overround. This calculator scales both probabilities down proportionally so they sum to exactly 100%.
If the fair probability for a team is 61% and Kalshi sells that team at 58¢, the exchange is cheaper than the book’s fair price before fees. Courtside runs this comparison across several books for every NBA game, using the Shin method, which accounts for the way books shade favorites and underdogs differently.
Common questions
What does no-vig mean?
No-vig odds remove the sportsbook’s built-in margin, leaving a fair probability for each side that adds up to 100%.
How is the vig calculated?
Convert each side’s odds to an implied probability and add them. Anything above 100% is the overround. A −110/−110 line has about 4.8% overround.
Which method does this calculator use?
Proportional normalization, the simplest method. Courtside’s board uses the Shin method across multiple books, which can differ slightly for heavy favorites.
How do I compare the result with Kalshi?
Kalshi prices are in cents, which equal percent. If the fair probability is above the Kalshi price plus fees, the exchange price is lower than the book’s fair value.