Enter odds for each outcome to calculate the bookmaker's overround, true probability per outcome, and fair (margin-free) odds.
Enter decimal odds for each outcome (2–6 outcomes supported).
Bookmaker Margin (Overround)
4.81%
Good — competitive margin.
| Outcome | Book Odds | Implied Prob | True Prob | Fair Odds |
|---|---|---|---|---|
| Home Win | 2.10 | 47.62% | 45.43% | 2.20 |
| Draw | 3.40 | 29.41% | 28.06% | 3.56 |
| Away Win | 3.60 | 27.78% | 26.50% | 3.77 |
For informational and entertainment purposes only. Please gamble responsibly. 18+
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Bookmaker margin (also called overround or vigorish) is the built-in profit edge added to a market. If the true probabilities of all outcomes sum to 100%, a bookmaker prices them so the implied probabilities sum to more than 100%. The excess — expressed as a percentage — is the margin. It is how bookmakers guarantee profit over time regardless of the outcome.
Margins below 3% are considered excellent and typically found on major 1X2 football markets at top bookmakers or exchanges. Margins of 3–6% are standard for competitive markets. Above 8% is high and often seen in exotic markets or smaller bookmakers. Exchanges like Betfair offer margins closer to 2% but charge commission on winnings.
Enter the same market odds from two different bookmakers and compare the resulting margin. The bookmaker with the lower margin is giving you better value overall. Over hundreds of bets, even a 1–2% margin difference can make a significant impact on long-term profitability.
Implied probability is the raw conversion of each set of odds (1/decimal × 100). These sum to more than 100% because of the margin. True probability scales each implied probability proportionally so all outcomes sum to exactly 100%, effectively stripping the margin. Fair odds are the decimal equivalent of the true probability.
Yes — this calculator supports up to 6 outcomes, covering markets like correct score ranges, Asian handicap lines, or any multi-way market. Add outcomes with the button and enter each set of odds. The margin calculation works the same way regardless of the number of outcomes.
