Odds and math
No-vig odds
Also called fair odds, de-vigged odds
To remove the vig, convert both sides of a market to implied probabilities, add them, and divide each by the total so they sum to exactly 100%. Two prices of −110 become 50% and 50%; a −200 / +170 market becomes roughly 64.4% and 35.6%.
These fair probabilities are the correct benchmark for any bet. A price that beats the fair number is a good price; one that doesn't is you paying the house for an opinion.
The simple normalisation above is called the multiplicative method, and it slightly overstates heavy favourites. The power and Shin methods correct for that and matter most on lopsided markets and long-shot fields.
Want the full version? Read the in-depth guide, with worked examples and the math.
See also
- Vig — The bookmaker's built-in margin — the reason both sides of a market add up to more than 100%.
- Fair probability — The market's honest opinion — implied probability with the bookmaker's margin removed.
- Implied probability — The chance of an outcome as expressed by its odds, including the bookmaker's margin.