Body Fat Calculator

Estimate body-fat % with the US Navy method.

Estimate your body-fat percentage using the U.S. Navy circumference (tape-measure) method — no calipers or scales needed. Enter a few measurements to get your body-fat percentage, its fitness category and your fat vs lean body mass, in metric or US units. Runs fully in your browser — nothing is uploaded.

Body Fat Calculator features

How to use Body Fat Calculator

  1. Pick gender & units

    Choose male or female (the formula differs) and metric or US units for your measurements.

  2. Measure & enter height and neck

    Measure around the neck just below the larynx and enter it along with your height.

  3. Measure your waist (and hip)

    Measure the waist at the navel for men, and both waist and hip for women, keeping the tape snug but not tight.

  4. Add your weight

    Enter your weight so the tool can convert your body-fat percentage into fat mass and lean mass.

  5. Read your body fat

    See your estimated body-fat percentage, its fitness category and your fat vs lean body mass instantly.

Frequently asked questions

How accurate is the U.S. Navy body fat method?

It's typically within about 3–4% of a DEXA scan for most people — impressively good for a tape measure. Accuracy drops for very lean or very heavy bodies, but it's a reliable way to track changes over time.

How should I measure for the best result?

Use a flexible tape, keep it level and snug (not compressing the skin), and measure on bare skin. Neck goes just below the larynx; waist at the navel for men and the narrowest point for women; hips at the widest point for women.

What's a healthy body fat percentage?

For men, roughly 14–17% is fitness level and 18–24% average; for women, about 21–24% fitness and 25–31% average. Essential fat is ~2–5% (men) and ~10–13% (women) — going below that is unhealthy.

Why are the formulas different for men and women?

Women naturally carry more essential fat and distribute it differently, so the female formula adds a hip measurement and uses different constants to stay accurate.

What's the difference between BMI and body fat percentage?

BMI only uses height and weight, so it can't tell muscle from fat — a muscular person can have a high BMI but low body fat. Body fat percentage estimates the actual proportion of fat, a better measure of body composition. Use both together.

How often should I measure my body fat?

Every 2–4 weeks is enough to track a trend without being misled by day-to-day fluctuations. Measure at the same time of day, ideally in the morning, with the same tape technique each time so the numbers are comparable.

Is my data uploaded?

No. All calculations happen locally in your browser — your measurements are never sent anywhere.

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