How the Body Fat Calculator works
This calculator uses the US Navy Circumference Method, developed by Hodgdon and Beckett (1984). It uses body measurements to estimate body fat percentage without expensive equipment.
Men: BF% = 495 / (1.0324 − 0.19077 × log₁₀(waist−neck) + 0.15456 × log₁₀(height)) − 450
Women: BF% = 495 / (1.29579 − 0.35004 × log₁₀(waist+hip−neck) + 0.22100 × log₁₀(height)) − 450
Women: BF% = 495 / (1.29579 − 0.35004 × log₁₀(waist+hip−neck) + 0.22100 × log₁₀(height)) − 450
How to measure correctly
- Neck: measure just below the larynx (Adam's apple), sloping slightly downward
- Waist (men): at the navel level; Waist (women): at the narrowest point
- Hips (women only): at the widest point of the hips/buttocks
- Measure in the morning, standing straight, stomach relaxed
Body fat percentage categories
| Category | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athletic | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Obese | 25%+ | 32%+ |
How to use your results
If your body fat is in the Average or Obese category, focus on creating a moderate calorie deficit (400–500 kcal/day) combined with resistance training to lose fat while preserving muscle.
If you're in the Athletic or Fitness range, your goal might be body recomposition — building muscle while maintaining fat. This requires eating at maintenance with high protein (2g/kg).
Track your measurements every 4 weeks. The scale alone is misleading — body fat % and measurements tell a more accurate story of progress.
Frequently asked questions
How accurate is the US Navy body fat calculator?
The US Navy method has an accuracy of ±3–4% compared to DEXA scans. It's one of the most accurate field methods available, comparable to skinfold calipers when measurements are taken correctly.
What is a healthy body fat percentage?
For men: 10–20% is considered healthy (fitness to average range). For women: 18–28% is healthy. Athletes may be lower (6–13% men, 14–20% women). Essential fat minimum is 2–5% for men and 10–13% for women.
How do I reduce body fat percentage?
Create a moderate calorie deficit (400–500 kcal/day), maintain high protein intake (1.6–2.2g/kg body weight), do resistance training 3–4x/week, and include cardio 2–3x/week. Aim for 0.5–1% body fat reduction per month.
Can I have a normal BMI but high body fat?
Yes — this is called 'normal weight obesity' or 'skinny fat'. BMI doesn't distinguish between fat and muscle. A person can have BMI 22 (normal) but 30% body fat. Body fat % is a more accurate health indicator than BMI alone.
How long does it take to go from 25% to 15% body fat?
Losing 10% body fat typically takes 4–6 months with a consistent 500 kcal/day deficit and resistance training. For a 80kg man at 25% BF (20kg fat), losing 8kg of fat takes approximately 22–24 weeks.
Is the Navy method accurate for very muscular people?
Less accurate for very muscular individuals — large neck circumference in muscular people can underestimate body fat. DEXA scan or hydrostatic weighing is more accurate for athletes.
What is the difference between body fat % and BMI?
BMI uses only height and weight — it cannot distinguish muscle from fat. Body fat % directly measures the proportion of fat tissue. A bodybuilder may have BMI 30 (obese) but 8% body fat. BMI is a population screening tool; body fat % is more meaningful individually.
How often should I measure body fat?
Every 4 weeks is ideal. More frequent measurements are not useful as changes are too small to detect accurately. Always measure under the same conditions: morning, after bathroom, before food or exercise.