How the no-vig fair odds calculator works
Removing the margin from a market gives the bookmaker's own view of the true probabilities, and therefore a fair price for each outcome. This calculator strips the vig by scaling the implied probabilities so they add up to 100%.
- Convert each price to an implied probability and add them.
- Divide each implied probability by the total. The results sum to 100% and are the no-vig probabilities.
- Fair odds for each outcome are 1 divided by its no-vig probability.
Worked example
A two-way market at 1.91 and 1.91.
- Implied 52.4% each, total 104.7%.
- No-vig probability 50% each; fair odds 2.00 on both sides.
This is the multiplicative method, which spreads the margin in proportion. Bookmakers often load more margin onto the longer price, so other methods exist; the difference is small at short prices and grows at long ones.
Questions
- What do I do with the fair odds?
- Compare them with a price elsewhere. A bookmaker offering more than the fair price from a sharper market is offering value on that market's view.
- Which market should I de-vig?
- The sharpest one you can see, typically an exchange or a low-margin book, because its probabilities have been tested by the most money.
- Is this the same as the fair prices in the Proppr feed?
- No. The feed's fair odds come from projected performance, and its Market Average is a de-vigged average across bookmakers. This calculator de-vigs one market you type in.
