Body Composition calculators
Understand how your weight is distributed between fat, lean mass and skeletal structure.
3 calculators in this section
BMI Calculator
Body mass index with WHO and Asian-Pacific thresholds
Body Fat Calculator
Body fat percentage from tape measurements
Ideal Weight Calculator
Four clinical formulas, side by side
Why the three disagree
BMI needs only height and weight, which is why epidemiologists can run it across millions of people, and why it predicts population risk well while misreading plenty of individuals. Body fat from tape measurements adds what BMI cannot see: a waist reading captures visceral fat, the metabolically active kind that sits around the organs. The ideal weight equations are a different thing again. They were written for drug dosing in the 1970s and 80s, four are still in clinical use, and they can differ by six kilograms for the same person.
Body Composition guides
Body Recomposition: Losing Fat and Gaining Muscle at the Same Time
Losing fat while adding muscle is possible, but not for everyone equally. Here is who it works for, what the trials show, and why the scale stops being useful.
Ideal Body Weight Formulas Compared: Why Four Equations Give Four Answers
Devine, Robinson, Miller and Hamwi disagree by several kilograms at the same height. The reason is that none of them was built to describe a healthy weight.
Why Body Composition Formulas Use Different Equations for Men and Women
Navy, Deurenberg, Devine and Mifflin all carry a sex term. Here is the biology behind those terms, how large they are, and why a binary switch is a crude proxy.
Lean Body Mass: What It Is and Why It Drives Your Metabolism
Lean body mass is everything you are not carrying as fat, and it sets most of your resting energy expenditure. Here is how it is calculated and what it changes.
How to Measure Body Fat at Home: Methods Ranked by Accuracy
Calipers, tape, smart scales and BMI-based equations all claim to measure body fat. Here is how each one works, how wrong it typically is, and which to trust.
Body Fat Percentage vs BMI: Which Number Actually Matters?
Body fat percentage describes what your body is made of. BMI describes how heavy you are for your height. Here is when each one earns its place, and where both fail.