Body Fat Percentage Calculator

Body fat percentage calculator using the U.S. Navy circumference method. Enter sex, height, waist, neck, and hip (women) in metric or imperial units for an estimated body fat percentage to one decimal place. Measurements convert to inches internally before the logarithmic formula runs. Circumference-based estimate for personal tracking — not medical advice, diagnosis, or a laboratory measurement.

How to Use the Body Fat Percentage Calculator

Choose units and sex, enter height and circumferences, then Calculate for an estimated body fat percentage to one decimal place. Reset clears the form.

  1. Choose metric (cm) or imperial (ft/in for height; inches for circumferences).
  2. Select sex — this determines required measurements and the formula.
  3. Enter height, waist, and neck. Women also enter hip circumference.
  4. Press Calculate to see estimated body fat percentage to one decimal place.
  5. Use Reset to clear the form and try another measurement set.

Methodology

Men: Body Fat % = 495 ÷ (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450. Women: Body Fat % = 495 ÷ (1.29579 − 0.35004 × log₁₀(waist + hip − neck) + 0.22100 × log₁₀(height)) − 450. All measurements convert to inches first; waist − neck (men) and waist + hip − neck (women) must be positive.

Worked examples

  • Male 5′10″ (70 in), waist 34 in, neck 15 in → estimated ≈ 11.1% body fat.
  • Female 5′5″ (65 in), waist 28 in, hip 38 in, neck 13 in → estimated ≈ 2.9% body fat.
  • Measure at the same time of day with a level tape — snug, not compressing skin.

Common mistakes

  • Measuring waist at the wrong level (typically navel for Navy method consistency).
  • Entering waist ≤ neck (men) or waist + hip ≤ neck (women) — the log term becomes invalid.
  • Treating the estimate as a clinical diagnosis or exact DEXA equivalent.

Limitations

Circumference screening cannot capture individual muscle mass, bone structure, or all fat distribution patterns. Hydration and technique affect repeatability. Informational estimate only — not medical advice, diagnosis, or treatment guidance.

FAQ

What is body fat percentage?

Body fat percentage is the share of your total weight made up of fat tissue. This calculator estimates it from circumference measurements and height using the U.S. Navy method — an approximate reference, not a direct lab measurement.

How does the Body Fat Percentage Calculator work?

Select sex and unit system, enter height and required circumferences (waist and neck for men; waist, hip, and neck for women). The tool converts measurements to inches and applies the U.S. Navy formula, rounding the result to one decimal place.

What is the U.S. Navy body fat method?

The U.S. Navy method estimates body fat from height and body circumferences using logarithmic equations developed for population screening. This tool uses the Navy method only — not BMI, skinfold, or BIA estimates.

What measurements are needed for men?

Men need height, waist circumference, and neck circumference. Waist must be greater than neck so the formula’s logarithm argument is valid.

What measurements are needed for women?

Women need height, waist circumference, hip circumference, and neck circumference. Waist plus hip must be greater than neck for a valid calculation.

Why is hip measurement required for women?

The female U.S. Navy formula includes hip circumference in the log term: log₁₀(waist + hip − neck). It reflects differences in fat distribution compared with the male equation.

Can I enter measurements in centimeters?

Yes. Choose metric to enter height in centimeters and circumferences in centimeters. The calculator converts all values to inches internally before applying the formula.

How accurate is a circumference-based body fat estimate?

Circumference formulas provide useful planning references but cannot match DEXA, hydrostatic weighing, or other professional methods. Hydration, measurement technique, and individual body shape can shift results.

Is body fat percentage the same as BMI?

No. BMI uses height and total weight only. Body fat percentage here is estimated from circumferences and height via the U.S. Navy equations. They measure different aspects of body size and composition.

Is this calculator a medical measurement?

No. This is an informational circumference-based estimate, not a clinical diagnostic device or prescribed health assessment. Consult qualified professionals for personalized body-composition evaluation.