Overround
Convert every outcome to implied probability and add them. The amount above 100% is the bookmaker overround.
Example
Odds 2.10, 3.40 and 3.60 total about 104.81%, producing roughly 4.81% overround.
Normalization
No-vig probability = raw implied probability ÷ total implied probability. The adjusted market then totals 100%.
Limitations
Proportional normalization is transparent but real bookmakers may distribute margin unevenly.
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No-Vig & Margin CalculatorFrequently asked questions
Is overround guaranteed profit? — No; it is a pricing advantage.
Can a market total below 100%? — Yes, due to arbitrage, stale prices or missing outcomes.