Find the tool you need
Search across calculators, planners, checkers and reference tools. Results appear as you type.
Why this site exists
Every week brings a small question that needs a proper answer. How much paint will a room take? Is a mortgage overpayment worth making? How much storage will a CCTV system need? What size pagefile makes sense on a particular Windows computer?
The answer is often a calculation rather than an opinion. The Useful Site brings those calculations together in one place, without asking you to create an account or hand over personal details first.
Most tools run entirely inside your browser. You enter the figures, the page performs the calculation and the result stays on your device. Where a result is only an estimate, the page says so and explains the assumptions behind it.
Browse by subject
Start with the subject closest to the problem you are trying to solve.
Useful places to start
These tools cover some of the questions people regularly need to answer at home, at work or while planning a project.
What makes a useful calculator?
A clear purpose
You should be able to tell what a tool does before entering a single figure.
Visible assumptions
An estimate is only helpful when you know what it assumes and where it can go wrong.
Plain English
Technical language is sometimes necessary, but it should be explained rather than used to impress.
No account barrier
You should not need a password, subscription or profile simply to perform a calculation.
Privacy by design
Where possible, your entries remain in the browser and are not sent to the website.
Room to improve
Mistakes can happen. The site makes it easy to report something unclear or suggest a better approach.
A site built around practical problems
The Useful Site started from the sort of calculations that crop up in ordinary life and IT support: paint coverage, storage capacity, network speeds, household costs and the occasional question that would otherwise end up on a scrap of paper.
It has grown into a broader collection, but the test for every page remains the same: does it help somebody reach a sensible answer?
Some calculations are exact. Others depend on typical rates, published guidance or values supplied by the user. Health, finance and forensic-science pages are presented as educational tools rather than substitutes for professional advice. The relevant page should make that distinction clear.
Questions about The Useful Site
Do I need an account?
No. There is no registration process and no account is required to use the calculators.
Are the tools free?
Yes. Advertising helps cover the cost of running the site, but the calculators themselves are free to use.
Are my entries stored?
The calculators are designed to work in your browser. The figures you enter are not deliberately saved as calculator records or attached to a user account.
Are all results exact?
No. Some tools perform exact arithmetic, while others provide estimates based on the values, rates or assumptions shown on the page.
Can I report an error?
Yes. The Contact page explains how to report a mistake or unclear explanation.
Can I suggest a new tool?
Yes. Use the Suggest a Tool page. Every suggestion is considered, although not every idea will be added.
Something missing?
Found a calculation you keep doing by hand? Tell me what would make it useful and how you currently work it out.