Probability Calculator
Convert odds into a clear win probability in seconds. Just enter the odds for or odds against an outcome, and the calculator instantly shows the percentage chance to win and the percentage chance to lose—so you can understand risk at a glance. It also computes the implied probability and converts the same odds into fractional odds automatically.
Result
| No of possible event that occured | ||
|---|---|---|
| No of possible event that do not occured |
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Use this Probability Calculator to compare the chances of outcomes when two events can happen. It helps you answer common questions fast, without long formulas.
For example, if event A has a 50% chance and event B also has a 50% chance, the calculator can show the opportunity of:
- Both A and B are happening
- Only A happening
- Only B happening
- At least one happening
- Neither happening
The tool also includes six main results. If you enter how many times the experiment repeats (like rolling a die many times), you get six more results. That makes it easy to compare one try vs many tries in seconds.
How to Use the Probability Calculator
Our probability calculator helps you find the chances of different outcomes when you have two independent events (A and B). Follow these simple steps to get accurate results in seconds.
Choose the problem you want to solve
Start by writing your question clearly. Then reduce it into two separate events.
Example:
- Event A: “It rains today.”
- Event B: “I take an umbrella.”
Tip: This calculator works best when events are independent (one event does not change the chance of the other).
Find the probability of each event.
Estimate the chance of each event happening on its own. You can use past data, averages, or a known probability.
You only need two values:
- P(A) = probability of event A
- P(B) = probability of event B
Enter the percentages in the calculator.
Type P(A) and P(B) into the input fields. As soon as you enter them, the calculator will instantly show the likelihood of six key scenarios:
- Both events happen (A and B)
- At least one happens (A or B)
- Exactly one happens (A or B, but not both)
- Neither happens
- Only A does not occur (not A, but B happens)
- Only B does not occur (A happens, but not B)
You can also select “Show all” to view every result at once.
Calculate outcomes across multiple trials.
If you enter the number of times the experiment repeats (the number of trials), the probability calculator can also show six extra scenarios, such as:
- A happens every time
- A never happens
- A happens at least once
- B happens every time
- B never happens
- B happens at least once
You can change the trial count anytime, and the calculator will update automatically. That is useful when you want to test “what-if” situations—like finding what P(B) must be to make the chance of both events happening equal to 50%.
When probabilities are very small
Sometimes the chance of success is tiny, such as P(A) = 0.0001. In these cases, using scientific notation (like 1×10⁻⁴) helps you read and compare values without losing track of zeros.