Everyday utility

Probability Calculator

Calculate the probability of an event, its complement, and combined probabilities for multiple events. Use this Data and utilities tool to enter your numbers, review the result, and understand the key assumptions before making the next decision.

What you get
A focused calculator, clear explanation, common questions, and useful next tools.
Quick intro
Calculator
Result
Explanation
Common questions
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How this calculator works
The result depends on the numbers you enter and the assumptions shown below.

Probability = favorable outcomes / total outcomes. Ranges from 0 (impossible) to 1 (certain). Complement P(not A) = 1 − P(A). For independent events: P(A and B) = P(A) × P(B).

Review the inputs carefully and treat the output as an estimate. For decisions involving money, taxes, health, law, or security, compare the result with trusted professional guidance when needed.

Frequently asked questions

What is conditional probability?

P(A|B) = P(A and B) / P(B). It's the probability of A given that B has occurred. For independent events, P(A|B) = P(A).