# Probability Calculator

With the probability calculator you can investigate the relationships of likelihood between two separate events. For example, if the the chances of A happening is 50%, and the same for B, what are the chances of both happening, or only one, or at least one, or neither, and so on.

Below you'll discover:

- How to use the probability calculator properly
- How to find probability of single events

## How to use the probability calculator

To make the most of our calculator, you'll need to take the following steps:

**1. Define the problem you want to solve.**

Your problem will need to be condensed into two distinct events. If you want to calculate the probability of an event in an experiment with a number of equally possible trials, you can use the z-score calculator to help you.

**2. Find the probability of each event.**

The probability of a single event is known as its P-value. You'll find p-value calculator very useful.

**3. Type the percentage probability of each event in the corresponding fields.**

Once they're in, the probability calculator will immediately populate with the exact likelihood of 6 different scenarios:

- both events will happen
- at least one of the events will happen
- exactly one of the events will happen
- neither of the events will happen
- only the first event won't happen
- only the second event won't happen

The calculator will also show the probability of four more scenarios, given a certain number of trials.

- A always occurring
- A never occurring
- B always occurring
- B never occurring

## How to find probability of events

Again, the probability of a single event is called it's P-value, and you can express it as such:

- The probability of A =
`P(A)`

- The probability of B =
`P(B)`

The basic definition of probability is the ratio of the number of a chosen outcome to the total number of all possible outcomes. So, if you want to know the probability of picking a red marble out of a bag of 50 marbles where only 10 are red, the answer will be one in 5, `1/5`

, or `20%`

.

We use intuitive calculations of probability all the time. Knowing how to quantify likelihood is essential for statistical analysis. It allows you to measure this otherwise nebulous concept called "probability".

## Further reading

If you're interested in applications of the probability theory, make sure to check out the risk calculator and the relative risk calculator.