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Implied Probability Calculator
An implied probability calculator that converts American, decimal, or fractional odds to a win percentage. See the probability the sportsbook is pricing in.
How to Use This Calculator
What is an implied probability calculator?
An implied probability calculator converts a sportsbook's odds into the percentage chance the book is pricing into the line. It is the bridge between raw odds and the math of expected value: every meaningful question in sports betting starts with knowing what probability the sportsbook is assigning to each outcome.
For a moneyline at -110, the implied probability is approximately 52.38%. For a bet at -110 to have positive expected value, the bettor's estimate of the true probability must exceed 52.38%.
Formulas
\[
\begin{aligned}
\text{Implied Probability (positive odds)} &= \dfrac{\strut 100}{\strut (\text{Odds} + 100)} \\[6pt]
\text{Implied Probability (negative odds)} &= \dfrac{\strut -\text{Odds}}{\strut (-\text{Odds} + 100)} \\[6pt]
\text{Implied Probability (decimal odds)} &= \dfrac{\strut 1}{\strut \text{Decimal Odds}}
\end{aligned}
\]
Worked example
A team is listed at -150 on the moneyline.
\[
\begin{aligned}
\text{Implied Probability} &= \dfrac{\strut 150}{\strut 250} \\[6pt]
\text{Implied Probability} &= 0.6000 \ \text{or} \ 60.00\%
\end{aligned}
\]
The sportsbook is treating the team as a 60% favorite to win, including the vig. The no-vig probability would be slightly lower, depending on the price of the other side.
Why implied probability matters for sports bettors
Implied probability is the foundation of every sports betting decision. Every question worth asking, including whether a bet is +EV, whether the line is moving for a reason, and whether the price is good, comes back to comparing the implied probability against an estimate of true probability.
Implied probability also makes vig visible. When the implied probabilities of all outcomes in a market are added together, the amount above 100% is the sportsbook's hold. Markets with wider hold leave less value for the bettor.
For the full math walkthrough, read our Implied Probability guide. Pair this calculator with the No Vig Calculator to see fair odds with the vig removed.
Common mistakes
- Treating implied probability as true probability. Implied probability includes the vig. The no-vig probability is what the book actually thinks the true probability is.
- Using implied probability without removing vig before comparing to a model. Your model output is a fair probability with no vig built in. Comparing it to a vigged implied probability misstates your edge.
- Confusing American odds conversions. Positive and negative American odds use different formulas. The calculator handles both, but the manual math is a common source of error.
- Ignoring the format of the odds. Decimal odds of 2.00 imply 50 percent. American odds of +200 imply 33.33 percent. Confusing the formats produces wildly wrong probabilities.
Frequently Asked Questions
What is an implied probability calculator?
An implied probability calculator converts a sportsbook's American, decimal, or fractional odds into a percentage chance of winning. The output reveals what probability the bookmaker is pricing into the line, including the vig.
How do you calculate implied probability?
For positive American odds, divide 100 by the odds plus 100. For negative American odds, divide the absolute value of the odds by that value plus 100. For decimal odds, divide 1 by the decimal odds.
\[
\begin{aligned}
\text{Positive odds:} \quad \text{Implied Probability} &= \dfrac{\strut 100}{\strut (\text{Odds} + 100)} \\[6pt]
\text{Negative odds:} \quad \text{Implied Probability} &= \dfrac{\strut -\text{Odds}}{\strut (-\text{Odds} + 100)} \\[6pt]
\text{Decimal odds:} \quad \text{Implied Probability} &= \dfrac{\strut 1}{\strut \text{Decimal Odds}}
\end{aligned}
\]
A line of -150 implies 60.00%. A line of +200 implies 33.33%.
How is implied probability different from true probability?
Implied probability is what the sportsbook is pricing into the line, including the vig. True probability is the actual underlying probability of the outcome. Implied probability is a public number that any bettor can calculate; true probability is unknowable, only estimable.
Why do implied probabilities of both sides sum to more than 100%?
Because of the sportsbook's vig. The amount above 100% is the bookmaker's commission. Removing it gives the no-vig implied probabilities, which sum to exactly 100%. Use the No Vig Calculator to see the fair odds with the vig removed.
Can I bet against implied probability for profit?
Only when the true probability of an outcome systematically exceeds the implied probability the sportsbook is offering. That is the core of +EV betting.
Does this calculator include the vig?
Yes. The implied probability returned by this calculator is the raw implied probability calculated directly from the odds, which includes the sportsbook's commission. To strip the vig out and see the fair odds, use the No Vig Calculator.
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