How the no-vig calculation works
Convert each price to its implied probability, add them up, then scale them back to 100%. The amount over 100% is the vig.
fair probability = implied probability ÷ sum of implied probabilities
Example: -110 / -110
Each side implies 52.38%, a total of 104.76%. Scaling back gives 50.00% each, so the fair price is +100 on both sides and the book's hold is 4.55%.
Example: -250 / +200
The vig here is 4.76%. The multiplicative method makes the favorite -214 and the underdog +214. The power method takes more off the underdog: -228 and +228.
Found a better price than the fair odds? Check its value with the EV calculator.
FAQ
What does no-vig mean?
No-vig odds are a market's prices with the sportsbook's margin taken out, so the implied probabilities add up to exactly 100%. A standard -110/-110 line implies 104.76% in total; the extra 4.76% is the vig.
Which method should I use?
Multiplicative is the standard and works well for evenly matched markets. Power removes more of the vig from the longshot, which better reflects how books tend to shade prices on heavy favorites against underdogs.
What's the difference between vig and hold?
Vig (overround) is how far the implied probabilities exceed 100%. Hold is the share of all money bet that the book keeps if action is balanced. At -110/-110 the vig is 4.76% and the hold is 4.55%.
How do I use fair odds?
Fair odds are the benchmark for finding value: if another book offers a better price than the fair odds from a sharp market, that bet has positive expected value. Plug both into the EV calculator to size the edge.