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Body-Fat Calculator

Estimate your body-fat percentage with nothing but a tape measure, using the U.S. Navy circumference method. See your lean and fat mass and where you sit on the fitness scale.

Units
Sex
kg
cm
cm

Just below the larynx, tape sloping slightly down at the front.

cm

At the narrowest point, relaxed.

cm

At the widest point of the buttocks.

Body fat30.6%Average
30.6%
EssentialAthleticFitnessAverageHigh
Lean mass54.1 kgMuscle, bone, organs, water
Fat mass23.9 kgWhat a deficit should target
The Navy method is accurate to about ±3–4% versus a DEXA scan. Measure at the same time of day, unflexed, and track the trend rather than any single reading. Saving this to your profile unlocks the Katch-McArdle formula in the calorie calculator.

How the Navy method works

Developed by the Naval Health Research Center in the 1980s, the method uses a logarithmic regression on neck, waist (and for women, hip) circumferences and height. It was validated against underwater weighing across a large, diverse sample. It is the same test used for military fitness standards precisely because it is fast, cheap and repeatable.

Why body fat matters more than weight

The scale cannot tell muscle from fat. When you lose weight without resistance training, up to a quarter of the loss can be lean tissue. Tracking body fat alongside weight tells you whether your deficit is doing its job. Combine this tool with the protein calculator and read why lifting while dieting matters.

Frequently asked questions

How accurate is the Navy method?

Validation studies put its error at roughly ±3–4 percentage points compared with DEXA, similar to consumer bioimpedance scales and better than most visual estimates. Its real strength is tracking change over time with the same tape.

How do I measure correctly?

Use a flexible tape, snug but not compressing the skin. Neck: just below the larynx. Waist: men at the navel, women at the narrowest point. Hips (women): the widest point of the buttocks. Measure relaxed, standing, after a normal exhale.

What is a healthy body-fat percentage?

For men, 10–20% is lean-to-fit and up to about 24% is average. For women, essential fat is higher, so 18–28% is lean-to-fit and up to about 31% is average. Very low levels are not healthier and can disrupt hormones.

Should I use this instead of BMI?

Use both. BMI is a screening number; body fat tells you what your weight is made of. If BMI says overweight but body fat is in the fitness range, trust the body fat.

Go deeper

Nutrition On a GLP-1 Medication? Protein and Muscle Matter More, Not Less How GLP-1 medications change appetite, why under-eating protein costs you muscle, practical protein, fiber, and fluid targets, and nausea-friendly foods. Nutrition How Much Protein You Actually Need to Lose Fat The evidence-based protein range for fat loss (1.6–2.2 g/kg), why it protects muscle and curbs hunger, how to spread it across meals, and what to eat. Mindset How to Weigh Yourself Without Losing Your Mind Daily weigh-ins and weekly averages turn a noisy scale into a useful tool. Learn what causes the swings, how to read the trend, and when to stop weighing.

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Ethereal provides general educational information and estimates only. It is not medical advice and does not replace an assessment by a doctor or registered dietitian. Do not use it if you are under 18, pregnant, or have a history of disordered eating without professional guidance. Read the full disclaimer.