About FitCalcKit

FitCalcKit is a free collection of health and fitness calculators built for everyday goals — losing weight, gaining muscle, running faster and feeling better.

What We Offer

We turn the formulas used by dietitians, coaches and sports scientists into simple tools anyone can use. No sign-ups, no downloads, no fees. Type in your numbers, click Calculate, and get your answer instantly.

Our calculators cover three areas: body composition (BMI, body fat, ideal weight), nutrition (BMR, TDEE, calories, macros, protein, water) and training (one rep max, running pace, heart rate zones). Each page explains how the tool works, shows the exact formula, and answers the most common questions.

How the Tools Are Built

Every calculator uses published, peer-reviewed methods: the Mifflin-St Jeor equation for basal metabolic rate, the U.S. Navy circumference method for body fat, the Epley equation for one rep max, and the Tanaka formula for maximum heart rate. Where formulas differ, we show you several and explain the difference.

Your Privacy

Everything runs in your browser. The numbers you enter never leave your device — we do not store, transmit or share them. See the Privacy Policy for details.

Important Disclaimer

FitCalcKit is not a medical service. All results are estimates for general information and education only. They are not a substitute for professional medical advice, diagnosis or treatment. Always consult a qualified healthcare professional before making significant changes to your diet, exercise or lifestyle.

Get in Touch

Found a bug, have an idea for a new calculator, or just want to say hi? Reach us on the Contact page — we read every message.