Body Fat Calculator
Estimate your body fat percentage using the US Navy tape-measure method with waist, neck, and hip circumferences. Free in your browser.
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How to use Body Fat Calculator
- 1
Enter your height, waist, and neck circumferences in centimeters.
- 2
If female, enter your hip circumference measurement.
- 3
Click Calculate to estimate your body fat percentage.
Capabilities
- Implements official US Navy circumference equations
- Tailored formula pathways for both biological males and females
- Instant client-side calculation using standard tape measurements
How Body Fat Percentage Is Estimated Using Circumference Methods
Body fat percentage reflects the proportion of total body mass composed of adipose tissue relative to lean mass (muscle, bone, water, and organs). Circumference-based models developed by the US Navy offer an accessible, equipment-free estimation of body composition.
Tape-measure formulas provide mathematical approximations. Variations in tape tension, hydration levels, and subcutaneous fat distribution introduce typical measurement variances of 3% to 4%. These values do not replace clinical body scans.
Formula: 86.010 * log10(waist - neck) - 70.041 * log10(height) + 36.76. Compares the abdominal circumference directly against neck thickness and overall stature.
Formula: 163.205 * log10(waist + hip - neck) - 97.684 * log10(height) - 78.387. Incorporates hip circumference to account for gynoid fat storage.
Worked Body Fat Example: Male (Height 170 cm, Waist 80 cm, Neck 38 cm)
Circumference Difference (Waist - Neck): 80 - 38 = 42 cm
Log Calculation: 86.010 * log10(42) - 70.041 * log10(170) + 36.76
Estimated Body Fat Percentage: 20.2%
Classification: This places the individual within the standard healthy fitness range for adult men.
To view height-to-weight ratios and WHO standard weight categories, use BMI Calculator.
This tool operates in a sandbox directly inside your web browser. All parsing, processing, and downloads are rendered locally. Your file size, metadata, and contents never cross the network. It works completely offline.
Frequently Asked Questions
How does the US Navy body fat formula calculate body composition?
The US Navy method uses circumference measurements (waist, neck, and hip for females) in logarithmic relation to height. It estimates body volume and density to infer total body fat percentage.
How should I measure my waist and neck accurately?
Measure your neck just below the larynx (Adam's apple) with the tape horizontal. Measure your waist horizontally at the narrowest point or at the navel level after a normal exhalation without compressing the soft tissue.
Why do females need a hip measurement for the calculation?
Biological females naturally store essential body fat across the pelvis and hips due to hormonal physiology. Including hip circumference improves mathematical modeling of female adipose tissue distribution.
How accurate is this tape-measure method compared to a DEXA scan?
The US Navy formula generally provides an estimate within 3% to 4% of dual-energy X-ray absorptiometry (DEXA) or hydrostatic weighing when tape measurements are performed carefully and consistently.
What is considered a healthy body fat percentage?
General fitness reference standards typically consider 14% to 24% healthy for men and 21% to 31% healthy for women. Essential physiological fat minimums are roughly 2% to 5% for men and 10% to 13% for women.