Bookmaker Margin & Fair Odds Calculator
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Enter the decimal odds for every outcome of a market. This tool shows the total book, the bookmaker's margin (overround / vig) and the fair, no-vig odds hiding behind the price. New to this? Read why betting odds never add up to 100%.
Enter odds to see the margin.
How it works
- Each outcome's implied probability = 1 ÷ its decimal odds.
- Add them all up — that's the total book. Above 100% by definition.
- The amount above 100% is the margin (overround / vig).
- Fair odds divide each implied probability by the total book so they add back to 100%, then take 1 ÷ that — the price with the margin stripped out.
Uses the proportional (multiplicative) no-vig method — the standard simple approach. Other methods (e.g. Shin) weight favourites and longshots differently. Calculations are exact from the odds you enter; always confirm live prices with the operator.
Want a single price in another format? Use the Odds Converter. Combining several bets? The Parlay Calculator shows how the margin compounds across legs. Comparing a bonus instead? Try the Bonus Value Calculator.
Related guides
- The bookmaker margin (vig) — what the margin is and why it matters.
- How betting odds work — read any odds format correctly.
- Value betting explained — spot odds priced in your favour.