Implied probability calculator
Enter the odds for every outcome of one event, in a 2-way or 3-way market. The calculator shows the probability each price implies, how much margin (vig or overround) the sportsbook has built in, and the no-vig fair odds once the margin is taken out.
The prices add up to more than 100%. The excess is the margin built into them; the fair prices below take it out pro rata.
- Total implied probability
- 104.71%
- Margin (overround)
- 4.71%
| Outcome | Implied | Fair | Fair odds |
|---|---|---|---|
| 1 | 52.36% | 50.00% | 2.000 |
| 2 | 52.36% | 50.00% | 2.000 |
Implied probability
A price of 2.00 implies a 50% chance, a price of 4.00 implies 25%. The implied probability is 1 divided by the decimal odds. It is what the price says, not a measurement of how likely the outcome really is.
Bookmaker margin: vig and overround
Add up the implied probabilities of every outcome of one event at one sportsbook. The total is normally above 100%, and the excess is the margin. For example, 1.91 on both sides of a two-way market implies 52.36% each: a total of 104.71%, a margin of 4.71%.
No-vig fair odds: removing the margin
The calculator removes the margin pro rata: each implied probability is divided by the total, so the fair probabilities add up to exactly 100%. In the example both sides become 50% and the fair odds 2.00. This is one simple method. It assumes the margin sits evenly on every outcome, which sportsbooks do not always do.
When the total is below 100%
If the best prices from different sportsbooks add up to less than 100%, the margin is negative: that gap is an arbitrage. Use the arbitrage calculator to see how the stake would be split, and read the risks in the arbitrage betting guide before relying on it.
Frequently asked questions
What is overround?
Overround is the amount by which the implied probabilities of all outcomes add up to more than 100%. It is the sportsbook's built-in margin, often called the vig or juice.
What are no-vig odds?
No-vig odds, or fair odds, are the prices left after the sportsbook's margin is removed, so that the probabilities of all outcomes add up to exactly 100%. This calculator removes the margin pro rata, which is one simple method.
Is implied probability the real chance of winning?
No. It is the probability the price implies, margin included. Removing the margin gives fairer numbers, but neither is a measurement of the true chance.
How do I calculate implied probability from American odds?
Convert to decimal first: +150 is 2.50 and -200 is 1.50. Then divide 1 by the decimal odds: 40% and 66.67%. The odds converter does this for you.
Can the total be below 100%?
At a single sportsbook it almost never is, because that would guarantee the bettor a profit. Across two or more sportsbooks the best prices sometimes add up to less than 100%, which is what arbitrage betting looks for.
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