Body Fat Calculator

About this tool

What is the Navy method for estimating body fat?

The U.S. Navy body fat formula uses circumference measurements to estimate body fat percentage. For men it uses neck, waist, and height; for women it adds hip circumference. The formula uses logarithms of the measurement differences, which correlates well with more precise methods like DEXA scanning. It is generally more accurate than the BMI method because it accounts for body shape rather than just weight and height.

How does the BMI-based body fat estimate work?

The BMI method uses the Deurenberg formula to convert BMI, age, and sex into an estimated body fat percentage: % fat = (1.20 × BMI) + (0.23 × age) − (10.8 × sex) − 5.4, where sex is 1 for male and 0 for female. It is convenient because you only need weight and height, but it is less accurate for muscular individuals — athletes may be overestimated — and for older adults.

What are healthy body fat percentage ranges?

For men: Essential fat 2–5%, Athlete 6–13%, Fitness 14–17%, Average 18–24%, Obese 25%+. For women: Essential fat 10–13%, Athlete 14–20%, Fitness 21–24%, Average 25–31%, Obese 32%+. Essential fat is the minimum required for basic physiological function. Dropping below it is dangerous. Optimal levels depend on your individual goals and medical history.

How should I take circumference measurements correctly?

Measure the waist at the narrowest point (usually just above the navel) while relaxed — do not suck in your stomach. Measure the neck just below the larynx (Adam's apple) with the tape horizontal. Measure hips (women only) at the widest point around the buttocks. Use a flexible tape measure, keep it snug but not compressing the skin, and take each measurement twice and average the results for accuracy.

Is this calculator a substitute for medical advice?

No. These are statistical estimates based on population-level equations. Individual results vary, and athletes, older adults, and people with unusual body proportions may see less accurate results. This tool is for educational purposes only. Always consult a qualified healthcare professional before making significant health or lifestyle decisions.