About Calculatto

Calculatto is a collection of 19 free calculators for the questions people actually look up: what your BMI is, what a loan will really cost, how old someone is in days, what you need on a final exam. Each one gives the answer in seconds and then explains the maths behind it, with your own numbers substituted into the formula, so you can check it yourself.

How it works

Everything runs in your browser. Nothing you type is sent to a server, stored, or tied to an account — close the tab and it’s gone. The only thing remembered on your device is a preference like metric versus imperial.

Formulas come from the standard sources for each field: the World Health Organization’s BMI bands, the Mifflin-St Jeor equation for calories, the US Navy circumference method for body fat, the ordinary amortisation formula for loans and mortgages, and so on. The “About” section on every calculator names the method and its limits.

What’s here

• Health — body, diet and fitness numbers (4 tools)
• Education — grades, gpas and percentages (4 tools)
• Finance — loans, savings and everyday money (4 tools)
• Math — percentages, averages and fractions (3 tools)
• Date & Time — ages, differences and countdowns (3 tools)
• Conversion — units of length, weight, temperature and more (1 tool)

A note on accuracy

These tools are for general information. Health results are screening numbers, not a diagnosis; financial results leave out fees, taxes and insurance unless stated; academic conversions follow common conventions that your institution may not use. For anything that matters, confirm with a professional or the body that sets the rules.

Missing something?

Suggest a calculator and we’ll consider it for the next batch. You can also reach us at hello@calculatto.com.