Body Fat Percentage Calculator
Estimate your body fat % using the accurate US Navy Method — no expensive equipment needed. Just a tape measure.
Your Measurements
Your Results
Body Fat % Categories
| Category | Men |
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How the Navy Method Works
The US Navy Body Fat Formula was developed by Hodgdon and Beckett in 1984 and is still widely used by military organizations and fitness professionals. It estimates body fat by measuring the circumference of specific body parts and applying a logarithmic formula. Unlike BMI, it accounts for body composition rather than just weight-to-height ratio.
For men: BF% = 495 / (1.0324 − 0.19077 × log(waist − neck) + 0.15456 × log(height)) − 450
For women: BF% = 495 / (1.29579 − 0.35004 × log(waist + hip − neck) + 0.22100 × log(height)) − 450
How to Measure Correctly
- Waist: Measure horizontally at the navel level. Don't suck in your stomach.
- Neck: Measure just below the larynx (Adam's apple), angled slightly downward at the front.
- Hips (women only): Measure at the widest point of the buttocks.
Everything About the Body Fat Calculator
The US Navy method formula, how to take accurate measurements, and what your numbers actually mean.
How It Works
- Select biological sex (different measurement points)
- Enter height, waist circumference (at navel), and neck circumference
- Women also enter hip circumference at the widest point
- Calculator applies the US Navy formula and returns BF%
- Compare your result to healthy range tables by age and sex
The Formula
Men: 86.01 × log₁₀(waist − neck) − 70.04 × log₁₀(height) + 36.76
Women: 163.205 × log₁₀(waist + hip − neck) − 97.684 × log₁₀(height) − 78.387
All measurements in inches. Accuracy is ±3–4% vs DEXA gold standard — better than visual estimates or BMI alone.
Pro Tips
- Measure in the morning before eating — consistent timing reduces variability
- Take 3 measurements at each site and average — tape placement changes results by ±1–2%
- Waist is measured at the navel, not the narrowest point
- DEXA scan (~$50–$100) is the most accurate method — do once per year to calibrate your tape measure results
Frequently Asked Questions
How accurate is the Navy body fat formula? +
The US Navy circumference method has a margin of error of roughly ±3–5% vs. DEXA scans (the gold standard). Hydrostatic weighing and Bod Pod are also accurate alternatives. Despite the imprecision, the Navy method is excellent for tracking trends — even if your absolute body fat is slightly off, consistent measurements in the same conditions will reveal whether you're gaining or losing fat over time. Measure in the morning before eating or exercising for best consistency.
What's the difference between BMI and body fat percentage? +
BMI is calculated from height and weight only — it can't distinguish between muscle and fat mass. A muscular athlete can have a BMI of 28 ("overweight") with 12% body fat, while a sedentary person can have a normal BMI of 23 with 30% body fat ("skinny fat"). Body fat percentage directly measures adipose tissue and lean mass, making it a much better indicator of health and fitness than BMI alone.
What is essential fat and why is it critical? +
Essential fat supports organ protection, bone marrow function, nerve insulation (myelin), and hormone production. In women, it plays a crucial role in reproductive function — women with body fat below 12–14% often experience amenorrhea (loss of menstrual cycle). For men, falling below 3–4% causes serious hormonal and metabolic disruption. The competitive bodybuilder look (2–5% for men) is impressive but not sustainable long-term.
How do I reduce body fat safely? +
Create a moderate calorie deficit (300–500 cal/day for 0.5–1 lb/week loss), prioritize protein (1.6–2.2g per kg body weight) to preserve muscle while losing fat, do resistance training 2–4 times per week, get 7–9 hours of sleep (sleep deprivation increases fat-storing hormones like cortisol and ghrelin), and manage stress. Avoid very low-calorie diets that sacrifice lean muscle mass for quick weight loss.
Does where you store fat matter for health? +
Yes, significantly. Visceral fat (stored around organs, revealed as a larger waist circumference) is metabolically active — it releases inflammatory cytokines and fatty acids directly into the portal circulation. This is strongly linked to insulin resistance, type 2 diabetes, cardiovascular disease, and metabolic syndrome. Subcutaneous fat (under the skin) is less harmful. Waist circumference >40 inches (men) or >35 inches (women) is a red flag regardless of total body fat percentage.