How do you calculate no-vig odds?

Convert each side to an implied probability, add them up, and divide each by the total. The results sum to 100%; turn them back into odds for the fair price of each side.

How much vig is in −110 / −110?

The two sides imply 104.76% together, an overround of 4.76%. On a balanced book that is a hold of 4.55% of the money staked.

Do prediction markets have vig?

Not as a bookmaker’s margin, but the gap between the YES and NO prices does the same job, and most exchanges also charge a trading fee. Removing the spread from the prices gives the market’s fair probability; the fee is a separate cost on the trade.

Tools

No-vig fair odds calculator

What do these odds say the probability is, once the bookmaker’s margin is taken out? Enter both sides of a line — or YES and NO prices from a prediction market — and the calculator returns the fair probability and fair odds for each side, and how much margin the line carries.

No-vig fair odds calculator

Odds formatOutcomesOutcome AOutcome B

Outcome A: 50.0% fair (52.4% with vig) · +100 · decimal 2.00
Outcome B: 50.0% fair (52.4% with vig) · +100 · decimal 2.00
Vig: 4.55% hold · 4.76% overround

The formula

fair p = implied p ÷ Σ implied p · hold = 1 − 1 ÷ Σ implied p

Why the probabilities add up to more than 100%

Each price implies a probability: −110 implies 110 ÷ 210 = 52.4%. Quote both sides of a game at −110 and they imply 104.8% between them. The extra 4.8 points is the overround; on a book balanced at those prices the operator keeps 1 − 1 ÷ 1.048 = 4.55% of the money staked, which is the hold, or vig.

A prediction market has the same thing in a different form. YES at 62¢ and NO at 40¢ add to 102¢: the 2¢ is the spread between buying and selling, which our lesson on YES and NO prices explains. Reading 62¢ as 62% overstates YES slightly; 62 ÷ 102 = 60.8% is the fair reading.

How the vig is removed

This calculator uses the multiplicative method: each implied probability is divided by their total, so the sides keep their proportions and sum to exactly 100%. It is the most common method and the right default for evenly matched two-way lines.

On lopsided lines and longshots, bookmakers tend to load more of the margin onto the longshot, so the proportional method can leave the favourite slightly undervalued. Other methods (additive, power, Shin) shift the margin differently and give answers a point or two apart at the extremes.

Frequently asked questions

How do you calculate no-vig odds?: Convert each side to an implied probability, add them up, and divide each by the total. The results sum to 100%; turn them back into odds for the fair price of each side.
How much vig is in −110 / −110?: The two sides imply 104.76% together, an overround of 4.76%. On a balanced book that is a hold of 4.55% of the money staked.
Do prediction markets have vig?: Not as a bookmaker’s margin, but the gap between the YES and NO prices does the same job, and most exchanges also charge a trading fee. Removing the spread from the prices gives the market’s fair probability; the fee is a separate cost on the trade.

Not financial advice. These calculators do arithmetic on the numbers you enter; they do not know a platform’s current prices or whether it is open to you. Check both in the platform reviews.