About Numora
Numora is a collection of free online calculators and converters for everyday questions: how much is that after tax, what will this loan cost, how many working days are left, how many cups is that in litres.
Why Numora exists
Many calculator sites give you a number and nothing else. That is fine until the result looks surprising and you cannot tell whether you made a mistake. Numora tries to do two things at once: give a quick answer, and explain it well enough that you can check it. Every tool page shows the formula, a worked example, how to read the result, common mistakes and answers to frequently asked questions.
What you will find
- 84 tools across maths, finance, conversions, health estimates, dates, text and utilities.
- Guides that explain the ideas behind the calculators, such as compound interest, loan payments, VAT, unit conversions, dates and password safety.
- Year-by-year tables for compound interest and loans, and quick reference tables for every converter.
How the tools work
Each calculator is a small program that runs in your browser. You enter the values, press the button and the result appears immediately. No account is needed, nothing is uploaded, and the same page works on a phone, a tablet and a desktop. Where a result depends on a figure that changes, such as an exchange rate or a tax rate, you enter it yourself instead of relying on a figure that may be out of date.
How the explanations are written
Tool pages follow a consistent structure: what the tool does, the formula in words and symbols, a worked example with real numbers, how to read the result, when to use it and which mistakes to avoid. Guides go further and connect several tools, with numbered steps, comparison tables and answers to common questions. The aim is that a reader can repeat any example by hand or in a spreadsheet and arrive at the same figure.
Privacy by design
Calculations run in your browser. The numbers and text you type are not sent to our server and are not stored by us. The site uses analytics and advertising services, which are described in the privacy policy. If you prefer, you can block cookies in your browser without losing access to the calculators.
Accuracy and corrections
Formulas come from standard references and are applied consistently. Results are estimates, because a calculator can only work with the values it is given and with the assumptions printed on the page. When an error is reported and confirmed, the tool or the text is corrected and the page is updated. The methodology page explains the process in more detail.
Limits you should know about
Results are for general information and support, not professional advice. Financial, tax, legal and health decisions should be checked with a qualified professional who knows your circumstances. Read the disclaimer for the full statement.
Get in touch
Spotted a mistake, or want a new tool? Visit the contact page or email us. Suggestions have shaped many of the tools on this site, and reports of wrong results are treated as a priority.