How it works
A price’s implied chance is the win rate at which a bet at that price breaks even: win that often, and over many bets the wins exactly pay for the losses. It is 1 ÷ the decimal price, whatever format the price is in.
Add up the implied chances of both sides of a market and they come to more than 100%. The extra is the sportsbook’s margin, also called the vig or the juice. Give the calculator the other side’s price and it shows the margin, and this side’s chance with the margin taken out.
The formula
Minus price: chance = |A| ÷ (|A| + 100)−110 → 110 ÷ 210 = 52.38%
Plus price: chance = 100 ÷ (A + 100)+200 → 100 ÷ 300 = 33.33%
Any format: chance = 1 ÷ decimal
Margin = chance A + chance B − 100%
Margin out: chance A ÷ (chance A + chance B)
A worked NFL example
An NFL point spread at −110 on both sides, the standard spread price.
- Each side: 110 ÷ 210
- 52.38%
- Both sides together
- 104.76%
- The book's margin: the total past 100%
- 4.76%
- Each side with the margin out: 52.38% ÷ 104.76%
- 50.00%
So a bet at −110 has to win 52.38% of the time to break even, though the market’s fair view of each side is 50%. The 2.38 points between the two are what the margin costs. A heavier price asks for more: a −300 favorite implies 75.00%, so it has to win three games in four to pay its way.
Common mistakes
- Taking it as the book’s forecast. The implied chance has the margin in it, so on both sides it is higher than the chance the market really gives.
- Comparing your chance with the wrong number. To profit, your chance has to beat the implied chance at the price you actually get, margin and all. Beating the no-vig chance alone isn’t enough.
- Adding prices from different books or times. Two books’ best prices can add up to 100% or less. That isn’t a margin to take out; the calculator flags it so you can check the prices.
- Mixing up the margin and the hold. The 4.76% is how far the chances add up past 100%. What the book keeps from evenly split action at −110 both ways is a little less: 4.55% of the money staked.
In Unitley
Unitley shows the chance each price implies on every NFL game it covers, next to a no-vig chance from the consensus of the books it tracks. How Unitley gets its prices.