Model │ Math · Free tool
Vig & Fair Odds
Every posted price hides the bookmaker margin. Enter both sides of a market and see what's left once the vig is stripped: the fair no-vig price you actually have to beat.
Enter a price in any format, +120, 1.91 or 10/11.
Enter a price in any format, +120, 1.91 or 10/11.
Type either side in American, decimal or fractional odds.
- Overround ,
- Side A, fair odds ,
- Side A, fair win % ,
- Side B, fair odds ,
- Side B, fair win % ,
Where the margin hides
Convert both sides of a market to implied probabilities and add them up. A fair market would total exactly 100%. A real one always clears it, that excess is the overround, and the slice above 100% is the bookmaker's hold: the edge baked into the price.
- Overround
- The sum of both sides' implied probabilities. 104.8% means the book has priced 104.8 cents of probability into a one-dollar market.
- Hold
- The overround minus 100%, the bookmaker's theoretical margin on a balanced book. Tighter markets hold less; props and parlays hold far more.
- Fair odds
- The price with the margin removed, here by the proportional method. Each side's probability divided by the overround. The break-even line. Beating the posted price isn't enough, you need to beat the fair one.
The proportional de-vig assumes the margin is split evenly across both sides. It is the standard quick estimate; heavy favourites can carry a little more of the margin than this method shows.