Body Fat Calculator
Estimate body fat percentage from tape measurements.
Frequently Asked Questions
How does the US Navy method work?
It uses logarithmic formulas based on neck, waist (and hip for women) and height, developed by the US Navy in the 1980s. It estimates body density, which converts to body fat percentage via the Siri equation.
How accurate is it?
Compared with DEXA scans, the Navy method is typically within about 3 to 4 percentage points when measurements are taken carefully at the right landmarks and the tape is snug but not compressing the skin.
Where exactly do I measure?
Measure the neck just below the larynx, the waist horizontally at the navel (men) or narrowest point (women), and hips at the widest point. Take each measurement twice and average it.
Is the Body Fat Calculator free, and is my data private?
Yes. It is completely free and every calculation runs locally in your browser, so the numbers and dates you enter are never uploaded, stored, or shared with anyone.
Related Tools
BMI Calculator
Calculate Body Mass Index and understand your health status.
Ideal Weight Calculator
Find your ideal body weight using the Devine and Robinson formulas plus the full healthy BMI weight range for your height, all shown side by side.
Calorie Calculator
Calculate daily calorie needs with the Mifflin-St Jeor equation, activity multipliers and goal targets for losing, maintaining or gaining weight.
Water Intake Calculator
Calculate your recommended daily water intake from body weight, exercise time and climate, shown in litres, millilitres and glasses per day easily.