About Calcly
Calcly is a free collection of online calculators and everyday tools, built for people who want a quick, honest answer — not a sign-up form.
We started Calcly because the big calculator sites are slow, crowded with ads and hard to use on a phone. Our goal is simple: tools that work instantly, explain their maths, and respect your privacy.
How our calculators work
Every calculator on this site runs entirely in your browser. Your numbers are never sent to a server, stored or sold. Each tool shows its formula and a worked example so you can check the result yourself.
Our sources
We use standard, named formulas: the Mifflin-St Jeor equation for calorie needs, the standard amortisation formula for mortgages and loans, the CDC weight categories for BMI, and the well-known 90-minute sleep-cycle model for the sleep calculator.
What we do not do
We do not give medical or financial advice. Health and finance results are estimates for general information only — see our Disclaimer. If you need personal advice, speak to a qualified professional.
Questions? Contact us.