Body Fat Percentage Calculator (U.S. Navy Method)
Estimate body fat percentage from neck, waist, and hip measurements using the U.S. Navy formula, with lean mass breakdown.
Medical disclaimer: This calculator is provided for educational and informational purposes only and does not constitute medical advice, diagnosis, or treatment. Results are general estimates and may not reflect your individual circumstances. Always consult a qualified healthcare professional before making decisions about your health.
Body Fat Percentage Calculator (U.S. Navy Method)
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Formula: BF% (Male) = 495 / (1.0324 - 0.19077 x log10(waist - neck) + 0.15456 x log10(height)) - 450
Worked example — Body Fat: 17.4% | Fat Mass: 31.4 lbs | Lean Mass: 148.6 lbs | Category: Fitness
Formula
BF% (Male) = 495 / (1.0324 - 0.19077 x log10(waist - neck) + 0.15456 x log10(height)) - 450
The U.S. Navy method calculates body fat percentage using circumference measurements in centimeters. For males: uses height, waist, and neck. For females: uses height, waist, neck, and hip. The formula derives body density from the ratio of these measurements using logarithmic equations, then converts density to body fat percentage. Fat mass = weight x BF%, Lean mass = weight - fat mass.
Worked Examples
Example 1: Male Body Fat Estimation
Problem:Male, 5'10" (70 inches), waist 34 inches, neck 15 inches, weight 180 lbs.
Solution:Convert to cm: Height = 177.8 cm, Waist = 86.4 cm, Neck = 38.1 cm Navy formula (male): 495 / (1.0324 - 0.19077 x log10(86.4 - 38.1) + 0.15456 x log10(177.8)) - 450 = 495 / (1.0324 - 0.19077 x 1.684 + 0.15456 x 2.250) - 450 = 495 / (1.0324 - 0.3213 + 0.3478) - 450 = 495 / 1.0590 - 450 = 17.4% Fat mass: 180 x 0.174 = 31.4 lbs Lean mass: 180 - 31.4 = 148.6 lbs
Result:Body Fat: 17.4% | Fat Mass: 31.4 lbs | Lean Mass: 148.6 lbs | Category: Fitness
Example 2: Female Body Fat Estimation
Problem:Female, 5'5" (65 inches), waist 30 inches, neck 13 inches, hip 38 inches, weight 140 lbs.
Solution:Convert to cm: Height = 165.1 cm, Waist = 76.2 cm, Neck = 33.0 cm, Hip = 96.5 cm Navy formula (female): 495 / (1.29579 - 0.35004 x log10(76.2 + 96.5 - 33.0) + 0.22100 x log10(165.1)) - 450 = 495 / (1.29579 - 0.35004 x 2.145 + 0.22100 x 2.218) - 450 = 495 / (1.29579 - 0.7508 + 0.4902) - 450 = 495 / 1.0350 - 450 = 28.3% Fat mass: 140 x 0.283 = 39.6 lbs Lean mass: 140 - 39.6 = 100.4 lbs
Result:Body Fat: 28.3% | Fat Mass: 39.6 lbs | Lean Mass: 100.4 lbs | Category: Average
Example 3: Male circumference example
Problem:A male is 5'10", weighs 180 lbs, has a 34-inch waist, and a 15-inch neck.
Solution:After converting inches to centimeters, the Navy formula estimates body fat at about 17.4 percent. That corresponds to roughly 31.4 lbs of fat mass and 148.6 lbs of lean mass.
Result:Body fat: about 17.4% | Fat mass: about 31.4 lbs | Lean mass: about 148.6 lbs
Frequently Asked Questions
How does the Navy body fat method work?
The Navy method estimates body fat percentage from height and body circumferences. It is a practical field method when a DEXA scan or other lab-based test is not available.
What is a healthy body fat percentage?
Healthy ranges vary by sex, age, and activity level. Athletic users are usually lower, while general-population healthy ranges are higher. Body Fat Percentage Calculator (U.S. Navy Method) is best used to track changes over time instead of treating one number as a diagnosis.
What is the difference between fat mass and lean mass?
Fat mass is the portion of body weight that comes from stored and essential body fat. Lean mass includes muscle, bone, organs, water, and other non-fat tissue.
How can I lower body fat while preserving muscle?
A moderate calorie deficit, resistance training, adequate protein intake, and patience are the usual foundation. Very aggressive cuts often make it harder to keep lean mass.
Where do the constants 495 and 450 in the formula come from?
They come from the Siri two-compartment equation, which converts body density into a fat percentage. The circumference terms and logarithms in the denominator are a regression that predicts body density from tape measurements; the surrounding 495 divided by density minus 450 is the conversion step. The two compartments are fat, assumed to have a density near 0.900 grams per millilitre, and fat-free mass near 1.100. That assumption is where much of the method uncertainty originates.
What is the difference between visceral and subcutaneous fat?
Subcutaneous fat sits directly under the skin and is what a tape or a caliper mostly senses. Visceral fat sits deeper in the abdominal cavity, packed around the liver, intestines and other organs, and is the depot most strongly linked with metabolic risk. A circumference method returns one combined percentage and cannot separate them, although a large waist relative to hips is a rough hint that more of the total is visceral.
Why does height appear in the equation at all?
The same waist girth means very different things on a short frame and a tall one. Height acts as a scaling term so the regression compares abdominal size against overall body size rather than in absolute centimetres. Because it enters as a logarithm, it compresses the effect: doubling height does not double the correction. This is also why entering height in the wrong unit produces a result that is wrong but not obviously absurd, so check the unit toggle first.
How does this compare with skinfold caliper testing?
Both are field methods that predict body density and then convert it with a Siri-type equation, so they share the same underlying assumptions. Calipers pinch subcutaneous fat at set sites such as the triceps, suprailiac and thigh, and in trained hands can be a little more sensitive to small changes. They also demand practice and a consistent technician. Tape circumferences are far easier to reproduce on yourself, which usually matters more than raw method accuracy when you are tracking your own trend.
Can hydration or a large meal change the reading?
Yes, indirectly. Water retention, a full stomach and bloating all add centimetres at the waist, and the formula treats extra abdominal girth as extra fat. Salt intake, carbohydrate loading, menstrual cycle phase and recent training can all shift waist girth by a centimetre or more without any change in fat mass. Measuring first thing in the morning, fasted and after using the bathroom, removes most of this variation and makes successive readings comparable.
What is fat-free mass index and why do some people prefer it?
Fat-free mass index is lean mass in kilograms divided by height in metres squared, the same shape as BMI but applied only to non-fat tissue. It answers a question that a fat percentage cannot: how much lean tissue you actually carry for your frame. Two people can share a body fat percentage while one has far more muscle. Because Body Fat Percentage Calculator (U.S. Navy Method) already outputs lean mass, dividing it by height squared gives the index directly.
References
Reviewed for accuracy by Rahul Singh, Health & Wellness Specialist · Editorial policy
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