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What Is Implied Probability? Converting Odds to Probability
Last Updated: March 4, 2026
Implied probability is the conversion of betting odds into a percentage that represents the likelihood of an outcome occurring, as priced by the market. Every set of odds — American, decimal, or fractional — encodes a probability. Extracting that probability is the first step in identifying whether a bet offers value.
Key Takeaways
- Implied probability translates any odds format into a win percentage the market has priced in
- The sum of implied probabilities across all outcomes exceeds 100% because of the vig
- Comparing implied probability to your own estimate reveals positive or negative expected value
- Prediction market prices are direct implied probabilities with little to no vig built in
- Removing the vig gives you “no-vig” or “true” implied probability — the fair market price
How Do You Convert Odds to Implied Probability?
Each odds format uses a different formula. The math is straightforward once you know which formula to apply.
American Odds (Moneyline)
- Negative odds: Implied Probability = |Odds| / (|Odds| + 100)
- Positive odds: Implied Probability = 100 / (Odds + 100)
Decimal Odds
- Implied Probability = 1 / Decimal Odds
Fractional Odds
- Implied Probability = Denominator / (Numerator + Denominator)
The odds converter tool handles all three formats instantly.
What Does an Implied Probability Calculation Look Like?
Take a moneyline of -150 on a favorite. Using the negative odds formula:
150 / (150 + 100) = 150 / 250 = 0.60 = 60%
The sportsbook is pricing this outcome at a 60% chance of occurring. If you believe the true probability is 65%, you have a potential value bet. If you think it is closer to 55%, the line is overpriced.
Here is a reference table covering common American odds:
| American Odds | Decimal Odds | Fractional Odds | Implied Probability |
|---|---|---|---|
| -300 | 1.33 | 1/3 | 75.0% |
| -200 | 1.50 | 1/2 | 66.7% |
| -150 | 1.67 | 2/3 | 60.0% |
| -110 | 1.91 | 10/11 | 52.4% |
| +100 | 2.00 | 1/1 | 50.0% |
| +110 | 2.10 | 11/10 | 47.6% |
| +150 | 2.50 | 3/2 | 40.0% |
| +200 | 3.00 | 2/1 | 33.3% |
| +300 | 4.00 | 3/1 | 25.0% |
| +500 | 6.00 | 5/1 | 16.7% |
For a full breakdown of how to read each format, see how to read betting odds.
Why Do Implied Probabilities Add Up to More Than 100%?
In a fair coin flip, heads = 50% and tails = 50%. Total: 100%. But sportsbooks do not offer fair odds. A typical NFL spread might be priced at -110 on both sides. Each side carries an implied probability of 52.4%, totaling 104.8%.
That extra 4.8% is the vig — the sportsbook’s built-in margin. The higher the total above 100%, the more the book is charging. A market totaling 110% is far more expensive to bet into than one totaling 102%.
This overround means raw implied probabilities overstate the true chance of every outcome. To get a cleaner picture, you need to remove the vig.
How Do You Calculate No-Vig Probability?
No-vig probability strips the margin out to reveal the fair implied chance. The method is simple: divide each side’s implied probability by the total of all sides.
Example: A two-way market with -150 (60.0%) and +130 (43.5%).
Total implied probability: 60.0% + 43.5% = 103.5%
- Favorite no-vig: 60.0 / 103.5 = 57.97%
- Underdog no-vig: 43.5 / 103.5 = 42.03%
Total: 100.0%. The vig has been removed. The book’s true assessment is that the favorite wins roughly 58% of the time, not the 60% that the raw odds suggest.
No-vig probabilities are what sharp bettors compare against their own models. The gap between your estimated probability and the no-vig line is your edge — or lack of one.
How Does Implied Probability Work in Prediction Markets?
Prediction markets simplify this entire process. A contract trading at $0.65 means the market prices the event at a 65% probability. There is no vig to remove and no formula to apply — the price is the probability.
This direct relationship makes prediction markets a clean source of market-implied probabilities across politics, economics, sports, and current events.
The Odds Reference dashboard displays prediction market prices as probabilities — the direct equivalent of implied probability in sports betting, but without the vig embedded. You can compare these clean probabilities against sportsbook lines to identify discrepancies.
Where Does Implied Probability Fit in a Betting Framework?
Implied probability is the foundation. Once you can convert odds to a percentage, you can:
- Identify value — Compare the market’s implied probability to your own estimate
- Calculate expected value — Quantify the dollar amount of edge per bet
- Size positions — Feed your edge into the Kelly Criterion for optimal bet sizing
Without implied probability, you are betting blind. With it, you have the first quantitative filter for separating good bets from bad ones.
For more terms and concepts, see the prediction markets glossary.