About FitCalc

What this site is

FitCalc is a set of 51 small calculators for the numbers people actually track: body mass index, body-fat percentage, ideal weight, calories burned, macros, protein, hydration, one-rep max, heart-rate zones, sleep timing, pregnancy dates and more. Each one does a single job, loads instantly, and needs no sign-up, email or app install.

How the numbers are produced

Every calculator on this site runs entirely inside your browser. When you type your weight or a measurement, that value is processed by JavaScript on your own device. It is never sent to a server, because no server does the calculating. You can disconnect from the internet after the page has loaded and the calculators keep working.

That matters more than usual with health data. A weight, a waist measurement or a date of birth is personal information, and here it never leaves your computer — it cannot be logged, stored or sold, because it is never transmitted in the first place.

Where the formulas come from

Each calculator uses an established, published formula rather than an invented one — for example Mifflin-St Jeor for basal metabolic rate, the US Navy tape method for body fat, and the Tanaka equation for maximum heart rate. The page under each tool explains what that formula is, which inputs it needs, and where it stops being reliable.

We also tell you the limits. Population formulas are averages, not measurements of you: two people with identical height, weight and age can differ by 15 percent in measured metabolism. Treat every result as an informed starting point, then adjust based on your own real-world results.

Not medical advice

FitCalc provides general information for education and curiosity. It is not medical advice, diagnosis or treatment, and it does not replace an assessment by a doctor, dietitian or other qualified professional. Do not use these calculators to make decisions about medication, diagnosed conditions, or a pregnancy. See our full disclaimer.

Why it is free

The site is supported by advertising. Advertising is loaded only after you agree to it through the cookie banner, and the tools work exactly the same if you decline. We keep ads out of the working area of each calculator so they never interrupt what you are doing.

Corrections and requests

Found an error, or want a calculator that does not exist yet? Write to hello@fitcalchub.com. Corrections and reader requests are the main reason this site changes.