Disclaimer

Last updated: September 2026

Not medical advice

TheFitnessCalculator.com publishes general health and fitness information and free estimation tools. Nothing on this Site is medical advice, diagnosis or treatment, and using it does not create a doctor–patient relationship. Always seek the advice of your physician or another qualified health provider with any questions about a medical condition, a symptom, a medication, or before starting a diet or exercise programme. Never disregard or delay professional medical advice because of something you read here.

If you think you may have a medical emergency, call your doctor or your local emergency number immediately.

The calculators are estimates

Every calculator on this Site applies a published population formula to the numbers you type in. Those formulas were derived from studies of particular groups of people, and they carry real error bars for any individual:

• BMI compares weight to height. It cannot tell muscle from fat, so it misclassifies muscular athletes as overweight and can miss excess fat in older or less active people.
• Calories and TDEE use the Mifflin–St Jeor equation and an activity multiplier. Real metabolic rate varies between individuals of identical size, and activity multipliers are broad bands, not measurements.
• Body fat uses the U.S. Navy circumference method. It depends on tape placement and typically differs from a DEXA or hydrostatic measurement.
• Ideal weight reports the Devine and Robinson formulas, which were originally created for medication dosing rather than as health targets.
• Water intake is a rough body-weight-based estimate. Real needs shift with climate, illness, medication, pregnancy and kidney function.

These tools are intended for healthy, non-pregnant adults. They are not appropriate for children, for pregnant or breastfeeding people, for competitive athletes, or for anyone with a medical condition affecting weight, fluid balance or metabolism.

No guarantee of accuracy

We work to keep the formulas and explanations correct and current, but we make no warranty that the content is complete, accurate or up to date. You use this Site and its results at your own risk, and you are responsible for any decision you make based on them. To the fullest extent permitted by law, we accept no liability for any loss or harm arising from use of the Site.

Advertising

This Site is free to use and is supported by advertising. Adverts are supplied by third-party networks and their presence is not an endorsement of any product, service or claim. How advertising cookies work is described in our privacy policy.

External links

We sometimes link to outside research and health organisations for context. We do not control those sites and are not responsible for their content or their privacy practices.

Questions

If you spot an error in a formula or an explanation, please tell us through the contact page — corrections are welcome. See also our terms of use.