How to use the Probability Calculator
- Choose the type of problem.
- Enter the counts or probabilities (as decimals between 0 and 1).
- Read the probability, the odds and related results.
What does this tool do?
Probability measures how likely something is, from 0 (impossible) to 1 (certain). For equally likely outcomes it's simply favourable outcomes divided by total outcomes — 1 in 6 for rolling a particular number on a die.
For two independent events, P(A and B) = P(A) × P(B). For repeated independent trials, the binomial distribution gives the chance of exactly k successes, as well as at most or at least k.
Why use it?
- Three common problem types in one tool.
- Shows odds as well as probability.
- Binomial results for exactly, at most and at least.
The formula
Privacy
The calculation happens instantly in your browser. The numbers you enter are not sent to our servers or saved. There's no account to create and nothing to install.
Frequently asked questions
What does independent mean?
One event happening doesn't change the chance of the other — like two separate coin flips. Drawing cards without putting them back is not independent.
Last reviewed by the M2Toolkit team.