Body composition & BMI
Estimate your body fat percentage, or check your Body Mass Index against a healthy range.
Body Fat Calculator
Estimate your body fat percentage from tape measurements (U.S. Navy method) or your BMI.
Open tool FreeSleep Calculator
Find the best time to wake up or go to bed so you rise between 90-minute sleep cycles.
Open tool FreeBody Measurement Tracker
Log weight, waist, chest and more over time, chart your progress, and set goals — saved in your browser.
Open tool FreeWeight Loss Timeline
See how long to reach your goal weight — projected goal date, chart, and dated milestones from a rate or target date.
Open tool FreeBMI Calculator
Body Mass Index from height and weight, with your healthy-weight range. (In the Calculators suite.)
Open toolBMI vs body fat
BMI (Body Mass Index) is a quick proxy calculated from just your height and weight. It's useful for a fast, population-level check, but it can't tell muscle from fat — a muscular athlete and a sedentary person of the same height and weight can land on the same BMI while having very different body compositions.
Body fat percentage goes a step further and estimates your actual composition — how much of your weight is fat versus lean mass (muscle, bone, organs, water). The Body Fat Calculator gets there with U.S. Navy tape measurements, or a rougher BMI-based estimate when you don't have a tape measure handy. Use the BMI Calculator first for a quick screen, then the Body Fat Calculator for a closer look at composition.