Probability Calculator

Calculate basic probability for events. Free online probability calculator with AND, OR operations.

The Probability Calculator computes probabilities for single and combined events. Calculate the probability of A AND B, A OR B, NOT A, and conditional probabilities. Enter your event probabilities to find combined outcomes. Essential for statistics, games, risk assessment, and decision-making involving uncertain outcomes.

Common use cases

  • Game and gambling odds
  • Risk assessment
  • Insurance calculations
  • Statistical research
  • Decision theory applications

How to use

  1. Enter probability of event A
  2. Enter probability of event B (if needed)
  3. Select the operation (AND, OR, NOT)
  4. Click calculate for the result
  5. View the formula used

FAQ

What is probability?

A number from 0 to 1 representing the likelihood of an event. 0 = impossible, 1 = certain.

How do I calculate P(A AND B)?

For independent events: P(A AND B) = P(A) × P(B). For dependent events, use conditional probability.

How do I calculate P(A OR B)?

P(A OR B) = P(A) + P(B) - P(A AND B). The subtraction avoids double-counting overlap.

What is complementary probability?

P(NOT A) = 1 - P(A). The probability of an event not occurring.