ZeroFee Tools
Free body fat percentage calculator using the US Navy tape-measure method

ZeroFee Tools' free body fat calculator estimates your body fat percentage from simple tape measurements using the U.S. Navy circumference method. No calipers, no scale needed: just your height and a few circumferences, and you get your body fat %, category and lean body mass.

Your measurements

Measure waist at the navel (men) or narrowest point (women), neck below the Adam's apple, hips at the widest point. Keep the tape level and relaxed.

Note: Estimates are for information only and are not medical advice. Tape-measure methods have a margin of error; consult a health professional for clinical body composition assessment.

Frequently asked questions

How accurate is the Navy body fat formula?

Within about 3-4 percentage points of lab methods for most people, provided measurements are careful and consistent. It is less reliable at very high body fat levels or unusual fat distribution.

Where exactly do I measure my waist?

Men: around the navel. Women: at the narrowest point of the midsection. Keep the tape horizontal, breathe out normally, and do not suck in or compress the skin.

Do I need my weight for this calculator?

No, weight is optional. Body fat % comes from the tape measurements alone; weight only lets the tool also show fat mass and lean mass in kilograms.

Can I use inches instead of centimeters?

The fields accept centimeters; convert inches by multiplying by 2.54, or use our unit converter to switch quickly.

Why does the formula differ for men and women?

Fat distribution differs by sex, so the female equation adds hip circumference and uses different constants. Both versions were calibrated against underwater weighing data.

How does the US Navy body fat method work?

Short answer: The U.S. Navy method estimates body fat from circumference measurements instead of calipers or scans. For men it uses height, neck and waist; for women it adds hips. The values go into a logarithmic formula developed from hydrostatic weighing data.

Because it only needs a tape measure, it is the most practical at-home method. Typical accuracy is within 3-4 percentage points of lab methods when measurements are taken carefully and consistently.

What is a healthy body fat percentage?

Short answer: For men, roughly 6-13% is athletic, 14-17% fit, 18-24% average and 25%+ is classified as obese. For women, roughly 14-20% is athletic, 21-24% fit, 25-31% average and 32%+ is classified as obese.

Essential fat (the minimum for health) is about 2-5% for men and 10-13% for women. Ranges shift with age, and where you carry fat matters too: abdominal fat carries more health risk than hip and thigh fat.

Why measure body fat instead of just BMI?

Short answer: BMI cannot distinguish muscle from fat, so muscular people can score "overweight" while being lean, and slim people can carry excess fat. Body fat percentage measures composition directly, making it a better tracker for recomposition goals.

Use both together: BMI for a quick screen, body fat % for what is actually changing. If your weight stalls but your waist shrinks, you are likely gaining muscle while losing fat.

How to use this calculator step by step

  1. Select male or female (the formula differs by sex).
  2. Enter your height and tape measurements in centimeters.
  3. Add your weight too if you want fat mass and lean mass figures.
  4. Click "Calculate body fat" for your percentage and category.
  5. Re-measure monthly under the same conditions (morning, relaxed) to track trends.

You may also need

BMI CalculatorCompare your BMI category with your body fat reading. Calorie CalculatorSet calorie targets around your lean mass, not just weight. Age CalculatorHealthy body fat ranges shift with age - know yours.