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Probability Calculator

Calculates single and combined event probabilities — and, or, not, conditional — with results as fractions, decimals and percentages.

Calculators Nothing uploaded No sign-up Free, unlimited
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Enter your figures and press Calculate.
In short Probability Calculator is a free online tool on inputtesthub.com that calculates single and combined event probabilities — and, or, not, conditional — with results as fractions, decimals and percentages. It needs no account, no download and no payment, and there is no daily usage limit. Everything is processed inside your own browser, so the data you paste is never uploaded to a server.

How to use the Probability Calculator

  1. Enter your figures in the input fields.
  2. The result updates as you type, together with the full working.
  3. Check the breakdown table to see exactly how the number was reached.

About the Probability Calculator

The Probability Calculator calculates single and combined event probabilities — and, or, not, conditional — with results as fractions, decimals and percentages. It runs as plain JavaScript inside the page, which means there is no upload step, no queue and no size limit imposed by a server — the only limit is your own device.

What people use it for

  • Probability homework.
  • Working out combined risk of two events.
  • Understanding why "or" probabilities are not simply added.

Frequently asked questions

Is there a limit on how often I can use the Probability Calculator?
It is free, with no account, no trial and no daily cap. Every calculators tool on inputtesthub.com works the same way: open the page and use it.
Does anything I enter leave my computer?
No. The Probability Calculator runs entirely in your browser using JavaScript. Your input never reaches inputtesthub.com or any third party — open your browser's Network tab while you use it and you will see no request go out.
What do people use the Probability Calculator for most?
The most common reasons people reach for it: probability homework. Working out combined risk of two events. Understanding why "or" probabilities are not simply added. It is built for exactly those cases rather than being a general-purpose tool with this bolted on.
How precise is the result?
The calculation runs in double precision and the result is shown to ten significant figures, so converting a value and converting it back returns the original. What is displayed is rounded for readability; what is copied is not.

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