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Vig / Bookmaker Margin Calculator

Measure overround on a two-way market and see no-vig fair odds.

Book margin

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Worked result from default inputs (server-side math).

Side A implied	Side B implied	Overround	Fair A	Fair B
52.36%	52.36%	4.71%	50.00%	50.00%

Educational maths only. Not betting advice. Confirm live odds and terms with the operator. 18+.

What is bookmaker margin / vig?

The overround above 100% when you add implied probabilities from both sides of a two-way market. Lower margin usually means a sharper price.

Convert American, decimal, and fractional odds with implied probability.

Turn odds into win probability and reverse probability into fair odds.

Check if a sports bet is +EV using your win probability and the odds.