Vig Calculator

Vig (short for vigorish, also called juice or overround) is the margin a sportsbook or exchange charges on each bet. It ensures the book profits regardless of the outcome. Standard American odds of -110/-110 carry a 4.55% vig.

Convert each outcome to its implied probability (1 / decimal odds), sum them, and subtract 1. The vig percentage equals (overround - 1) / overround × 100. For example, -110/-110 implies 52.38% + 52.38% = 104.76%, giving a vig of 4.55%.

Most sportsbooks charge 4-5% vig on standard markets (like point spreads at -110/-110). Prediction markets like Polymarket and Kalshi often have lower effective vig (1-3%) due to their order-book structure, while prop bets and exotic wagers can carry 8-15% vig.

No-vig fair odds remove the bookmaker margin to show what the true odds would be in a perfectly efficient market. They are calculated by dividing each implied probability by the total overround, then converting back to odds format.

Vig is baked into the odds themselves (the prices already include the margin), while prediction market fees are explicit per-trade charges applied on top of the contract price. Both reduce your effective return, but they work through different mechanisms.

Lower vig means better pricing for bettors, but it does not guarantee a positive expected value. You still need an edge on the true probability. Low vig simply means less of your edge is consumed by the market maker.

Overround is the sum of all implied probabilities for every outcome in a market. A fair market sums to exactly 100%. Any amount above 100% represents the bookmaker margin. An overround of 104.76% means the book has a 4.55% vig.

Yes. Use the PM Cents mode to enter YES and NO contract prices directly (e.g., 52¢ and 52¢). The calculator will show the effective vig embedded in those prices, which represents the spread between the best bid and ask.