Calculate the bookmaker's built-in margin on any market and see the true fair odds for each outcome.
The overround (also called "vig" or "juice") is the bookmaker's built-in profit margin. If all outcomes were priced fairly, the implied probabilities would add up to exactly 100%. Bookmakers price them to total 105–115%, ensuring they profit regardless of the result.
A 5% overround means for every €100 wagered across a market, the bookmaker expects to keep €5 and return €95. The higher the overround, the worse the value for bettors.
Major football match results: ~5–8%. Horse racing (each-way): ~15–25%. Specials and novelty markets: up to 30%+. Betting exchanges typically have 2–4% total commission instead of built-in overround.