Body Fat Percentage Calculator (Navy Method)
The US Navy body fat formula uses waist, neck, hip (women only), and height measurements to estimate body fat percentage. It requires only a tape measure and is accurate to within 3–4% of DEXA scan results for most adults.
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Formula
Male: 86.010×log₁₀(waist−neck) − 70.041×log₁₀(height) + 36.76; Female: 163.205×log₁₀(waist+hip−neck) − 97.684×log₁₀(height) − 78.387
The Navy formula uses log₁₀ transformations of circumference measurements because the relationship between circumference and body fat is not linear — it is logarithmic. For males, waist minus neck represents abdominal girth net of musculature. For females, waist plus hip minus neck captures the pear-shape fat distribution pattern more accurately. The height logarithm adjusts for the scaling relationship between circumference measurements and total body volume.
How to use the Body Fat Percentage Calculator (Navy Method)
- 1
Enter your waist circumference
Value should be in inches.
- 2
Enter your neck circumference
Value should be in inches.
- 3
Enter your hip circumference (women only)
Value should be in inches.
- 4
Enter your height
Value should be in inches.
- 5
Enter your gender
- 6
Read your results instantly
Results update in real time as you type.
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Measuring for the Navy method
Measure waist at the navel (not the narrowest point) for men, and at the narrowest point for women. Measure neck just below the larynx (Adam's apple), sloping slightly downward to the front. For women, measure hips at the widest point of the buttocks. Use a soft measuring tape and ensure it is level all the way around. Do not suck in your stomach — breathe normally and measure at the end of a normal exhale. Take each measurement twice and use the average. Consistent technique is critical for meaningful comparisons over time.
Healthy body fat ranges
Healthy body fat ranges vary by sex and age. For men: essential fat 2–5%, athletes 6–13%, fitness 14–17%, acceptable 18–24%, obese 25%+. For women: essential fat 10–13%, athletes 14–20%, fitness 21–24%, acceptable 25–31%, obese 32%+. Women require more essential fat for hormonal health and reproductive function. Very low body fat in women can cause menstrual dysfunction and bone density loss. The Navy standard for military service is below 18% for young men and below 26% for young women.
Tips & Insights
Measure in the morning fasted
Abdominal circumference is lowest in the morning before eating. Consistent morning measurements reduce variability and make your trend line more reliable.
Use the same tape measure each time
Different tape measures can vary in tension. Using the same tape, taking measurements at the same time of day, and using the same technique ensures your readings are comparable across sessions.
Retest every 4–6 weeks
Body fat changes slowly — retesting more frequently than every 4 weeks rarely reveals meaningful change and may discourage you with normal daily variation rather than actual trends.
Worked Examples
Male: waist 34", neck 15", height 70"
Body fat ≈ 16.3% (fitness range)
Female: waist 30", neck 13", hip 38", height 65"
Body fat ≈ 24.1% (fitness range)
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Frequently Asked Questions
How accurate is the Navy body fat method?
Research shows error rates of 3–4% compared to DEXA scans for average-build adults. It tends to overestimate body fat in lean, muscular individuals and may underestimate in those with atypical fat distribution.
Do I need all four measurements for men?
Men only need waist, neck, and height. The hip measurement is only used in the female formula to account for lower-body fat distribution.
Is the log₁₀ formula used by the US military?
Yes. The US Department of Defense mandates this exact formula for body fat assessment during fitness tests for military service members.
What if my result seems too high or too low?
Re-check your measurements for consistency. Common errors include measuring waist at the wrong location (narrowest vs. navel), inconsistent tape tension, and rounding errors in the measurements.
How does this compare to caliper measurements?
Skinfold calipers require trained technique and are operator-dependent. The Navy tape measure method is more reproducible between users and is preferred for self-assessment despite being slightly less precise than a skilled caliper measurement.
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