What is body fat percentage?
Body fat percentage indicates what proportion of your total weight is fat tissue. It is a more accurate indicator than BMI for assessing body composition and health risk, because it distinguishes between muscle and fat.
A 180 cm man with a 90 cm waist and 40 cm neck gets approximately 18-20% body fat, within the average range (18-24%). The calculator applies the Navy formula with your exact measurements.
Navy method (US Navy)
This calculator uses the United States Navy method, which estimates body fat from circumference measurements:
%Fat = 495 ÷ (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450
%Fat = 495 ÷ (1.29579 − 0.35004 × log₁₀(waist + hip − neck) + 0.22100 × log₁₀(height)) − 450
Step-by-step example (man)
- Height = 180 cm, waist = 90 cm, neck = 40 cm
- log₁₀(90 − 40) = log₁₀(50) ≈ 1.699
- log₁₀(180) ≈ 2.255
- %Fat = 495 ÷ (1.0324 − 0.19077 × 1.699 + 0.15456 × 2.255) − 450 ≈ 18-20%
Body fat categories
Men
| Category | Percentage | |---|---| | Essential fat | 2-5% | | Athlete | 6-13% | | Fitness | 14-17% | | Average | 18-24% | | Obesity | 25%+ |
Women
| Category | Percentage | |---|---| | Essential fat | 10-13% | | Athlete | 14-20% | | Fitness | 21-24% | | Average | 25-31% | | Obesity | 32%+ |
- Waist: at navel level, without pulling the abdomen in
- Neck: below the larynx (Adam's apple)
- Hip: at the widest point of the buttocks
- Measure in the morning, before eating
Body fat vs BMI
BMI only considers weight and height, without distinguishing muscle from fat. A muscular person can have a high BMI but low body fat. That is why body fat percentage is a better health indicator, although BMI remains useful as a quick screening tool.
How to read the result
Essential fat is the minimum needed to live (2-5% men, 10-13% women); going below it is dangerous. Athlete and fitness ranges reflect athletic body composition; the average range is healthy for most people. If your result falls in obesity, small sustained changes (diet plus exercise) reduce cardiovascular risk.
The Navy method is an estimate from circumferences, not an exact measurement (like DEXA or hydrostatic weighing). The typical error margin is 3-5 percentage points. This tool is educational; consult a professional for precise assessment.
Frequently asked questions
The waist is measured at navel level without squeezing; the neck, just below the larynx. Measure in the morning before eating and without thick clothing for better accuracy.
For men, 14-24% is considered healthy; for women, 21-31%. Athletes are usually below those ranges.
BMI does not distinguish muscle from fat: a muscular athlete can have a high BMI with low fat. Body fat percentage measures body composition directly.
Related calculators
- BMI: quick weight-for-height screening
- Ideal weight: healthy weight range formulas
- Basal metabolism: calories burned at rest
- Daily calories (TDEE): adjust intake to your goal