Probability Calculator

The Probability Calculator works out the likelihood of an event, or combination of events, without you needing to remember the formulas. It's free to use and needs no sign-up, making it quick for students and anyone curious about odds. It's useful for homework problems, games of chance, or simply satisfying curiosity about how likely something is to happen.

Why use Probability Calculator?

Probability measures how likely an event is to occur, expressed as a number between 0 and 1 or as a percentage. For independent events, the calculator can multiply individual probabilities together to find the combined probability of both events happening, following basic probability theory. This removes the manual arithmetic and reduces the chance of a simple multiplication error changing your answer.

How to use Probability Calculator

1. Enter the number of favorable outcomes and total possible outcomes for a single event.
2. Add a second event if you want to calculate a combined probability.
3. View the calculated probability as both a decimal and a percentage.

Key features

• Calculates single-event probability from favorable and total outcomes
• Computes combined probability for two or more independent events
• Displays results as both decimals and percentages
• Free, instant, and requires no sign-up

Related tools

Explore statistics further with the Confidence Interval Calculator, review your data with the Average Calculator, or check ratios using the Percentage Calculator.

Frequently asked questions

Is Probability Calculator free?

Yes, the Probability Calculator is completely free with no sign-up required. You can calculate as many probability scenarios as you need.

What's the difference between single and combined probability?

Single-event probability looks at one outcome, like rolling a specific number on a die, while combined probability looks at the chance of two or more independent events all happening together. Combined probability for independent events is found by multiplying each individual probability.

Does this calculator handle dependent events?

The calculator is built around independent events, where one outcome doesn't affect the other, which covers most common probability questions like coin flips or dice rolls. For dependent events, where earlier outcomes change later odds, you would need to adjust the probabilities manually before entering them.

Can probability ever be greater than 1?

No, a valid probability always falls between 0 and 1, or equivalently between 0% and 100%. If your inputs produce a result outside that range, it usually means the favorable outcomes exceed the total possible outcomes and should be double-checked.