Probability Calculator — Events & Binomial
Single events, independent AND/OR, and the binomial distribution P(X=k)/P(X≤k)/P(X≥k). Client-side.
Single event
Two independent events
Binomial — P(X = k)
How to use
- 1 Single event: favorable outcomes ÷ total outcomes.
- 2 Two independent events: enter each probability for AND / OR.
- 3 Binomial: n trials, k successes, success probability p.
Why use this tool
- Three common probability problems in one place.
- Includes the binomial distribution P(X = k), P(X ≤ k) and P(X ≥ k).
- Runs entirely in your browser.
Frequently asked questions
How do I find a basic probability?
Divide the number of favorable outcomes by the total number of equally-likely outcomes.
What does “independent events” mean?
The outcome of one doesn’t affect the other. Then P(A and B) = P(A)·P(B), and P(A or B) = P(A) + P(B) − P(A)·P(B).
What is the binomial distribution?
The probability of exactly k successes in n independent trials each with success probability p: P(X = k) = C(n, k) pᵏ (1−p)ⁿ⁻ᵏ.
What are odds vs probability?
Probability is favorable ÷ total; odds are favorable : unfavorable. A probability of 1/4 is odds of 1 : 3.
What is Probability Calculator?
A probability calculator finds the probability of single and combined independent events (AND/OR) and the binomial distribution — the chance of k successes in n trials.
Probability Calculator is a free math utility by Zerethon Tools. Single events, independent AND/OR, and the binomial distribution P(X=k)/P(X≤k)/P(X≥k). Client-side. Runs entirely in the browser — no signup, no upload.
- Category
- Math
- Pricing
- Free
- Privacy
- Browser-based
- Signup
- Not required
Privacy
Your data never leaves your browser unless explicitly stated. Probability Calculator runs entirely client-side — no server upload, no logging, no tracking of your input.
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