Prediction Market De-Vig Calculator
Enter the yes and no prices to see the fair probability without the margin.
- Fair probability of no
- 44.7%
- Sum of the two prices
- 103¢
- Overround
- 3.00 points
- Fair yes price
- 55.3¢
- Fair no price
- 44.7¢
Proportional de-vig: each price divided by the sum, the same method as Bandwagon's Markets pages.
Educational tool. Bandwagon does not take or place wagers. Results are arithmetic on the numbers you enter, not advice.
How the prediction Market De-Vig Calculator works
If the yes and no prices sum to more than 100¢, the excess is the margin between the two sides' asks: the market's overround. The fair probability of yes is yes / (yes + no), and of no, no / (yes + no).
This is the proportional de-vig used on Bandwagon's Markets pages (docs/MARKETS.md): the prices of a set of mutually exclusive outcomes are divided by their sum so they add to 100%. A set with a price missing is never normalized, since that would hand the missing outcome's share to the others.
When the sum is below 100¢, buying both costs less than the $1 one of them pays; real markets rarely stay there long.
Prediction Market De-Vig Calculator example
You enter
- Yes price (cents)
- 57¢
- No price (cents)
- 46¢
You get
- Fair probability of no
- 44.7%
- Sum of the two prices
- 103¢
- Overround
- 3.00 points
- Fair yes price
- 55.3¢
- Fair no price
- 44.7¢
Yes at 57¢ and no at 46¢ add to 103¢, an overround of 3 points. Dividing each by 103 leaves a fair yes of 55.3% and a fair no of 44.7%.
Prediction Market De-Vig Calculator questions
What does de-vig mean for a prediction market?
Removing the gap between the two sides' prices so that the probabilities add to 100%.
Why do yes and no sometimes sum to more than 100?
Each is the price to buy that side, and the market's spread sits between them.
Which price should I use for the market's probability?
The midpoint of the bid and ask, or the de-vigged pair of asks. The Markets pages label which they show.
Does this work for more than two outcomes?
The same division works for any set of exclusive outcomes. This calculator takes a pair.
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