iGaming Glossary / Overround
What is Overround?
The built-in margin in a set of betting odds that gives the operator its edge. Also called the vig or margin.
The overround is the built-in margin an operator adds to a set of odds. If you add up the implied chances of every outcome in a market, a fair book would total 100 percent. The overround is the amount above that, and it is how the operator makes a profit over time.
For example, if all the prices in a market add up to 105 percent, the overround is roughly 5 percent. A lower overround means better value for you, because more of the true odds are passed back to the player rather than kept by the house.
The overround is also called the vig or the margin. Sharp bettors compare it across operators to find the best prices, since smaller margins improve long-term returns. It is the betting cousin of the casino house edge.
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