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Body Fat Calculator

Estimate your body fat percentage using two common approaches: the U.S. Navy circumference method and the Deurenberg BMI-based formula. Switch between metric and imperial units. All calculations run locally in your browser.

Estimate Body Fat %
Client-side onlyNo data leaves your browser
Method

Navy uses neck/waist (and hip for women). Deurenberg uses BMI, age, and sex.

Units
Metric
Sex & Age
years
Height
cm

Quick adjust: 175 cm

Weight
kg

Required for Deurenberg (BMI) method; optional for Navy method.

Circumferences (Navy)
cm
cm

Measure at the narrowest neck, the natural waist (or navel for men), and fullest hip for women.

Results

U.S. Navy22.7% • Average
Summary
  • Method: U.S. Navy circumference
  • Sex & Age: male, 30 y
  • Height: 175 cm
  • Weight: 72 kg
  • Neck: 38 cm
  • Waist: 84 cm
  • Estimated Body Fat: 22.7% (Average)

Navy (cm): Men = 86.010·log10(waist − neck) − 70.041·log10(height) + 36.76; Women = 163.205·log10(waist + hip − neck) − 97.684·log10(height) − 78.387.

Deurenberg: %BF = 1.20·BMI + 0.23·age − 10.8·sex − 5.4 (sex: male=1, female=0).

Interpretation

Categories (ACE): Men — Essential 2–5%, Athletes 6–13%, Fitness 14–17%, Average 18–24%, Obese ≥ 25%. Women — Essential 10–13%, Athletes 14–20%, Fitness 21–24%, Average 25–31%, Obese ≥ 32%.

These are screening estimates; consider professional assessment for accuracy (e.g., DXA, BIA).

How to Use the Body Fat Calculator

This free, Body Fat Calculator estimates your body fat percentage using two popular approaches. Use the U.S. Navy circumference method for tape-measure inputs or the Deurenberg BMI method when you have height, weight, age, and sex. No data is uploaded.

  1. Pick a method: Choose U.S. Navy (uses neck/waist and hip for women) or Deurenberg (BMI) (uses BMI, age, and sex).
  2. Select units: Choose Metric (cm, kg) or Imperial (ft/in, lb). You can switch anytime.
  3. Enter height & weight: Required for BMI method; height is also required for Navy.
  4. Add circumferences (Navy): Measure neck and waist (plus hip for women). Stand relaxed, measure horizontally, and keep the tape snug but not compressing the skin.
  5. Review your estimate: The calculator shows % body fat and a category (Essential, Athletes, Fitness, Average, Obese).
  6. Copy or reset: Use Copy to save your summary or Reset to start over.

Formulas

  • U.S. Navy (cm): Men = 86.010·log10(waist − neck) − 70.041·log10(height) + 36.76; Women = 163.205·log10(waist + hip − neck) − 97.684·log10(height) − 78.387.
  • Deurenberg: %BF = 1.20·BMI + 0.23·age − 10.8·sex − 5.4  (sex: male=1, female=0).

Measurement Tips

  • Measure at the same time of day for consistency.
  • Use a flexible tape; measure in front of a mirror if possible.
  • For waist, measure at the narrowest point (or navel for men).
  • For hip (women), measure at the fullest part of the buttocks.

FAQ

Which method is more accurate?

The Navy method often tracks changes well if measurements are consistent. Deurenberg is convenient but depends on BMI, which doesn’t separate muscle and fat. For clinical accuracy, consider DXA or professional assessments.

Is my data private?

Yes. This calculator runs entirely in your browser (client-side). Nothing is uploaded.

Why do results differ from smart scales?

Different devices use different models (e.g., BIA vs. tape/BMI formulas). Use one method consistently to track trends over time.

Disclaimer: These formulas provide estimates and are not medical diagnoses. Consult a qualified professional for personalized advice.