About Calculators Fit

Calculators Fit is a free set of health, fitness, nutrition and strength-training calculators, with the math behind every result explained step by step. Our goal is simple: help you understand your body and your training, not just hand you a number.

Why we built this

Most calculators online give you just a number and nothing else — no context, no formula, no way to tell whether the result makes sense. We do the opposite. For each tool we show the exact formula we use, the reference ranges that put your result in context, and a clear, plain-language explanation. That way you can understand the result, double-check it, and learn something along the way.

How each calculator is built

Every calculator is based on recognized formulas and guidelines — for example, the World Health Organization (WHO) classification for BMI, the Mifflin-St Jeor equation for basal metabolic rate (BMR), and similar standards for body fat, macros and training. We cite our sources, we check the numbers against the original references, and everything runs in your browser. The data you type in is never sent to a server or stored by us — your calculations stay on your own device.

An important note

These are estimation and planning tools. They do not replace a medical evaluation, the advice of a registered dietitian, or guidance from a qualified physical-education or training professional. If you have a health condition, are pregnant, or are starting a new diet or exercise program, talk to a professional first. Use the numbers here as a starting point, not as a diagnosis.

Who is behind it

Calculators Fit is an independent project and part of a small network of focused calculator microsites. It is maintained by a small team that cares about getting the math right and keeping the explanations honest and readable. The site is supported by advertising (Google AdSense), which is what keeps every tool completely free to use. We don't sell your data — see our Privacy Policy for the details.

Get in touch

Found an error, want a calculator we don't have yet, or have a suggestion to make a tool clearer? We'd genuinely like to hear from you. Visit our contact page or email us directly at contact@calculatorsfit.com. Your feedback is the main way these calculators get better.