WeBall
Fair probability
Also called fair price, fair odds
The market's honest opinion — implied probability with the bookmaker's margin removed.
Posted odds always imply more than 100% across a market, because the excess is how the book makes money. The fair probability is what remains after that margin is normalised away: the market's real estimate, stripped of its fee.
This is the number any bet should be judged against. Compare your estimate to the posted price and almost everything looks bad, because the posted price is deliberately worse than fair. Compare it to the fair price and you are measuring genuine disagreement.
WeBall computes it from cross-book consensus rather than a single sportsbook, so one book's aggressive line doesn't distort the baseline.
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%.
- No-vig odds — Odds with the bookmaker's margin normalised out, showing what the market actually believes.
- Model probability — WeBall's own estimate of how often a bet wins, before comparing it to any price.
- Edge — The gap between your estimated probability and the probability the price implies. Positive means value.