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繁體中文Bookmaker Margin Explained
Every set of odds has a built-in margin that lets the bookmaker profit over time. Understanding it helps you see why odds are slightly shorter than the true chance, and how to find better value. This guide explains it with hypothetical examples only.
- It is the edge built into odds, also called the overround or vig.
- Convert each price to implied probability (1 ÷ decimal odds), add them up, and the amount over 100% is the margin.
- Because the bookmaker builds a margin into prices.
What the margin is
The margin — also called the overround or vig — is the small edge baked into prices. It is why the implied probabilities of all outcomes add up to more than 100%.
How it shows up in odds
Convert each price to implied probability (1 ÷ decimal odds) and add them up. The amount over 100% is the margin.
Why it matters
The margin is the long-term cost of betting, like the house edge in casino games. Lower-margin markets give you better value, so comparing prices matters.
Finding better value
Tighter margins mean more of the true probability is paid back to you. Looking for shorter overrounds is part of value betting — comparing the implied probability of a price with your own estimate. See how odds work.
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🔞 18+ only. Examples are hypothetical and for explanation only — they are not betting advice or real odds. Please gamble responsibly.
FAQ
It is the edge built into odds, also called the overround or vig. It makes the implied probabilities of all outcomes add up to more than 100%.
Convert each price to implied probability (1 ÷ decimal odds), add them up, and the amount over 100% is the margin.
Because the bookmaker builds a margin into prices. That margin is the long-term cost of betting and the reason all implied probabilities sum to over 100%.
Last updated: 2026-06-15