Probability Calculator

Probability Calculator — Calculate Single & Multiple Event Probabilities Online

The Probability Calculator is a free online tool that quickly computes the probability of single events, the probability of two or more independent events occurring together, and conditional probabilities. Whether you are a student studying statistics, a data analyst modeling outcomes, a gambler evaluating odds, or a researcher conducting hypothesis testing, this calculator delivers fast, accurate results without any manual computation.

What Is Probability?

Probability measures how likely an event is to happen, expressed as a number between 0 (impossible) and 1 (certain), or as a percentage from 0% to 100%. The classical formula is the number of favorable outcomes divided by the total number of possible outcomes. For example, the probability of rolling a 6 on a fair die is 1÷6 ≈ 0.1667 or 16.67%. Real-world applications include weather forecasting, insurance pricing, machine learning, sports analytics, and risk management.

How to Use the Calculator

Enter the number of possible outcomes and the number of favorable outcomes for each event. The tool computes the probability of event A, event B, the intersection (A and B), the union (A or B), and the complement (not A). For independent events, the calculator multiplies probabilities; for mutually exclusive events, it adds them. Conditional probability P(A | B) is also available when you supply the joint probability.

Why Use Our Probability Calculator?

Calculating multi-event probabilities by hand invites mistakes — especially when working with fractions, percentages, or complement rules. This tool eliminates errors, runs entirely in your browser, and is mobile-friendly. It works for coin flips, dice rolls, card games, lottery odds, A/B testing, and any scenario involving discrete outcomes. Bookmark it for instant statistical computations anytime.

Tamer Baghdadi

CEO / Co-Founder