Simplicalcs is a collection of free, browser-based calculators built and maintained by Graham Frewin. Every tool is designed for people who need a quick, reliable answer without the faff — no sign-up, no paywall, no data sent anywhere. Every calculation runs locally in your browser the moment you type.
The tools span a wide range of everyday needs: personal finance, health, travel, specialist maths, and professional use. Alongside the expected — mortgage repayments, BMI, salary take-home — you'll find more specialist tools built for clinical and technical audiences, including renal function calculators using published medical formulae, electrical installation tools based on BS 7671, and cybersecurity scoring utilities. Each tool is chosen because existing options are either confusing, untrustworthy, or simply missing something obvious.
The design is deliberately plain. Generous text, plenty of space, and nothing competing with the thing you came to use. Tools that just do something are always preferred over tools that explain what they could do.
New tools are added regularly. If something you need isn't here yet, the feedback page is the fastest way to suggest it.
Want to add a calculator to your own site? Every tool on Simplicalcs is free to embed — paste one line of code, no sign-up required.