Body Fat Calculator

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Estimate your body fat percentage with the US Navy tape method from a few simple measurements, plus your fat mass, lean mass and category. Metric or imperial.

cm
kg
cm
cm
cm
Body fat – %
Category –
Fat mass –
Lean mass –
Uses the US Navy circumference method. Measure the waist at the navel for men and at the narrowest point for women; women also measure the hips. Results are an estimate and can vary by a few percentage points from clinical methods.

About Body Fat Calculator

The Body Fat Calculator estimates your body fat percentage using the US Navy circumference method. From your sex, height, weight and a few tape measurements — neck and waist for men, plus hips for women — it returns your body fat percentage, fat mass, lean mass and fitness category.

The Navy method uses logarithmic formulas built from circumference measurements: for men it combines waist minus neck with height; for women, waist plus hips minus neck with height. Fat mass is then your weight times the percentage, and lean mass is the remainder.

It is a practical alternative to calipers or DEXA scans when all you have is a tape measure. Categories run from essential fat through athletes, fitness and average to obese, giving your number context. Metric and imperial units are supported, free, in your browser.

How to use Body Fat Calculator

  1. Choose metric or imperial units and select your sex.
  2. Enter your height and weight.
  3. Measure and enter your neck circumference and waist circumference — at the navel for men, at the narrowest point for women.
  4. Women also enter the hip circumference at the widest point.
  5. Read your body fat percentage, category, fat mass and lean mass.

Frequently asked questions

It estimates body density from circumference measurements — waist and neck for men, waist, hips and neck for women — combined with height in logarithmic formulas, then converts density to a body fat percentage.

Measure the neck just below the larynx. Men measure the waist at the navel; women at the narrowest point, plus the hips at their widest. Keep the tape snug but not compressing, and measure without clothing where possible.

Typical ranges: men — 2–5% essential, 6–13% athletes, 14–17% fitness, 18–24% average, 25%+ obese; women — 10–13% essential, 14–20% athletes, 21–24% fitness, 25–31% average, 32%+ obese.

Fat mass is your total weight multiplied by your body fat percentage. Lean mass is everything else — muscle, bone, organs and water. Tracking both shows whether weight change comes from fat or muscle.

It is an estimate — results can differ from clinical methods like DEXA by a few percentage points, and measuring technique matters. Treat it as a general trend indicator, not medical advice; consult a professional for clinical assessment.
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