Body Fat Calculator

Estimate your body fat percentage using the US Navy measurement method - no gym equipment needed.

📏 What is Body Fat Percentage?

Body fat percentage is the proportion of your total body weight that consists of fat tissue. Unlike body weight alone or BMI, body fat percentage distinguishes between fat mass and lean mass, providing a far more complete picture of body composition and health risk.

Your body contains two types of fat: essential fat and storage fat. Essential fat is necessary for normal physiological function - it is found in bone marrow, organs, the central nervous system, and cell membranes. For men, essential fat is approximately 2–5% of body weight; for women, 10–13% (the higher amount supports reproductive function). Storage fat is the energy reserve accumulated in adipose tissue beneath the skin and around organs.

The US Navy method is one of the most practical and widely validated circumference-based formulas for estimating body fat percentage. Developed for use in military physical fitness assessments, it requires only a tape measure and takes under two minutes. It uses the relationship between body circumferences (waist, neck, and for women, hips) and height to estimate the percentage of body fat using a logarithmic formula.

Research comparing the US Navy method to DEXA scan results shows it is accurate to within 3–4 percentage points for most people, making it a reliable tool for tracking body composition trends over time even if the absolute number is not laboratory-precise.

Knowing your body fat percentage helps you set realistic fitness goals, assess health risks associated with excess body fat (such as metabolic syndrome, type 2 diabetes, and cardiovascular disease), and monitor progress during a diet or exercise programme more meaningfully than the scale alone.

📐 US Navy Body Fat Formula

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

waist = waist circumference in cm (measured at navel for men; narrowest point for women)

neck = neck circumference in cm (just below the larynx)

hip = hip circumference in cm at the widest point (women only)

height = standing height in cm

📖 How to Use This Calculator

Steps to Measure and Calculate

Select your gender - women have an additional hip measurement requirement.

Measure your height standing against a wall, in cm.

Measure waist circumference with a flexible tape measure. Men: measure at the navel. Women: measure at the narrowest point of the torso. Keep the tape horizontal and snug but not compressing skin. Take the average of three readings.

Measure neck circumference just below the larynx (Adam's apple), sloping slightly downward at the front.

Enter body weight to calculate fat mass and lean mass in kilograms. Then click Calculate.

💡 Example Calculations

Example 1 — Male, 175 cm, Waist 88 cm, Neck 38 cm, Weight 82 kg

log₁₀(88 − 38) = log₁₀(50) = 1.699

log₁₀(175) = 2.243

BF% = [495 ÷ (1.0324 − 0.19077 × 1.699 + 0.15456 × 2.243)] − 450 = [495 ÷ (1.0324 − 0.3241 + 0.3467)] − 450 ≈ 20.3%

Body Fat: 20.3% → Fitness category | Fat mass: 16.6 kg | Lean mass: 65.4 kg

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Example 2 — Female, 163 cm, Waist 72 cm, Hip 96 cm, Neck 32 cm, Weight 62 kg

log₁₀(72 + 96 − 32) = log₁₀(136) = 2.134

log₁₀(163) = 2.212

BF% = [495 ÷ (1.29579 − 0.35004 × 2.134 + 0.22100 × 2.212)] − 450 ≈ 26.8%

Body Fat: 26.8% → Average category | Fat mass: 16.6 kg | Lean mass: 45.4 kg

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Frequently Asked Questions

What is a healthy body fat percentage?+

Healthy ranges differ by sex and age. For men, 10–20% is generally considered healthy (athletes 6–13%, fitness 14–17%, average 18–24%, obese 25%+). For women, 20–30% is healthy (athletes 14–20%, fitness 21–24%, average 25–31%, obese 32%+). These ranges from the American Council on Exercise are widely referenced benchmarks.

How accurate is the US Navy body fat method?+

The US Navy method has a standard error of approximately 3–4 percentage points when compared to DEXA scan results. It is more accurate than BMI for estimating body composition but less accurate than laboratory methods like DEXA, hydrostatic weighing, or Bod Pod. It is an excellent free, equipment-free estimation for most people.

What measurements do I need for the US Navy method?+

For men: height, waist circumference (measured at the navel), and neck circumference. For women: height, waist circumference (at the narrowest point), hip circumference (at the widest point), and neck circumference. All measurements should be taken in centimetres or inches for consistency.

What is lean body mass?+

Lean body mass (LBM) is everything in your body that is not fat - muscles, bones, organs, blood, and water. It is calculated as total weight minus fat weight. Lean mass is important because muscle is metabolically active and maintaining or increasing it improves overall health, strength, and metabolic rate.

Can I reduce body fat without losing weight?+

Yes. Body recomposition - simultaneously gaining muscle while losing fat - is possible, particularly for beginners to resistance training, those returning after a break, or people who are overweight. It requires a slight calorie deficit or maintenance calories combined with progressive strength training and adequate protein intake (1.6–2.2 g per kg of bodyweight).

What is a healthy body fat percentage for women?+

According to the American Council on Exercise (ACE), healthy body fat for women is 21-24%. Athletes typically range 14-20%, fitness level 21-24%, average 25-31%, and obese 32%+. Women naturally carry more essential fat than men due to hormonal and reproductive functions. Body fat below 14% in women can disrupt hormonal function and menstrual cycles.

How accurate is the US Navy body fat formula?+

The US Navy circumference method has an accuracy of within 3-4 percentage points compared to DEXA (dual-energy X-ray absorptiometry), which is the gold standard. It can overestimate or underestimate for individuals with very high or very low muscle mass. For tracking changes over time, the Navy method is consistent and practical.

Does body fat percentage change with age?+

Yes. Body fat naturally increases with age even if body weight stays the same, because muscle mass tends to decrease after age 30 (sarcopenia) unless actively maintained through resistance training. The healthy body fat ranges cited by organisations like ACE account for this by having slightly higher acceptable ranges for older adults. Regular strength training and adequate protein intake are the most effective ways to slow this age-related change.

What is a healthy body fat percentage by age?+

For men: ages 20-39, healthy range is 8-19%; ages 40-59, 11-21%; ages 60-79, 13-24%. For women: ages 20-39, 21-32%; ages 40-59, 23-33%; ages 60-79, 24-35%. These are the American Council on Exercise (ACE) guidelines. Athletes typically fall 5-10% below these ranges. Essential fat (minimum for survival) is 2-5% for men and 10-13% for women.

🔗 Related Calculators

📌 Quick Tips

💡Measure your waist at the narrowest point (around the navel for men, smallest point for women) first thing in the morning before eating, and take three measurements, using the average.

💡The US Navy method has an error margin of roughly 3–4 percentage points. For clinical accuracy, DEXA scans or hydrostatic weighing are the gold standards.

💡Body fat percentage is more meaningful than body weight alone. Two people at the same weight can have very different health outcomes based on their fat-to-muscle ratio.