Your result
What your result means
With your measurements the circumference value used in the equation is 18.5 (waist minus neck for men; waist plus hip minus neck for women). Plugged into the Department of Defense formula with your height, that estimates 17% body fat — about 28.8 lb of fat and 141.2 lb of lean mass at your weight. Tape methods typically land within a few percentage points of lab measurements.
The math
Formula and sources
Men: %BF = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76 Women: %BF = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387 (all measurements in inches)
- log10
- base-10 logarithm (not natural log)
- height
- standing height
- waist, neck, hip
- circumferences, measured snug but not compressing the skin
Metric inputs are converted to inches before applying the equation. Military worksheets round the final value to a whole percent.
Sources we checked this against
- 1Army Body Composition Program – body fat calculation samplesU.S. Army · api.army.mil
- 2Evaluation of a circumference-based prediction equation to assess body composition (DoD equation)PubMed Central (NIH) · pmc.ncbi.nlm.nih.gov
Formula last checked 2026-11-04. Found an error? Tell us and we will fix it.
Step by step
Two worked examples
Army worksheet sample (man)
Estimated body fat
38.6%
- Sex
- Male
- Units
- US (ft, in, lb)
- Height (in, or cm if metric)
- 69
- Neck, below the larynx (in / cm)
- 16
- Waist (in / cm)
- 49
- Weight
- 230 lb
Waist − neck = 33. 86.010 × log10(33) − 70.041 × log10(69) + 36.76 = 38.6%; the Army sheet rounds this to 39%.
Army worksheet sample (woman)
Estimated body fat
47.3%
- Sex
- Female
- Units
- US (ft, in, lb)
- Height (in, or cm if metric)
- 64
- Neck, below the larynx (in / cm)
- 15
- Waist (in / cm)
- 42
- Hip, widest point (in / cm)
- 44
- Weight
- 190 lb
Waist + hip − neck = 71. 163.205 × log10(71) − 97.684 × log10(64) − 78.387 = 47.3%; rounded to a whole percent that is the Army’s 47%.
| Result | Example 1 | Example 2 |
|---|---|---|
| Estimated body fat | 38.6% | 47.3% |
| Fat mass | 88.7 lb | 89.9 lb |
| Lean mass | 141.3 lb | 100.1 lb |
Questions
Frequently asked questions
How do I measure correctly?
Measure on bare skin, standing relaxed. Neck: just below the Adam’s apple, tape sloping slightly down to the front. Waist: men at the navel, women at the narrowest point. Hip: around the widest part of the buttocks. Take each measurement twice.
How accurate is the tape method?
It is a population equation. Studies against DXA scans find typical errors of a few percentage points, and it can under- or over-estimate for very lean or very muscular people.
What is a healthy body fat percentage?
Ranges vary by age and sex, and there is no single official standard. Discuss your result with a clinician alongside waist size, blood pressure and lab tests.