Body composition calculator

Estimates body fat percentage from circumferences, calculates fat and lean mass and body mass index.

Free · No registration or payment

Unit system

Result

Body fat: 16.9 %
Fat mass: 12.7 kg
Lean mass: 62.3 kg
Body mass index: 24.5 kg/m²

Units: body fat in %, mass in kg, BMI in kg/m². Method source: the U.S. Navy formula (1984); body fat categories from ACE references, BMI categories from WHO.

Distribute these calories into protein, fat and carbs

Use your target calories to determine your macronutrients and hydration needs:

Daily calorie needs calculator (TDEE) →Macronutrient calculator →

The result updates as you change the fields. Your data never leaves the browser.

Only upon clicking, current data is sent to generate the PDF and is not stored.

How it is calculated

Body fat is estimated with the U.S. Navy method (Hodgdon and Beckett, 1984): it uses height and the circumferences of neck and waist, plus hips for women. The method was chosen because it needs no equipment and its error is comparable to consumer bioimpedance scales. BMI is calculated as well using the WHO classification — it says nothing about composition but allows comparison with population norms.

Formula

Men: %fat = 495 / (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450; Women: %fat = 495 / (1.29579 − 0.35004 × log₁₀(waist + hip − neck) + 0.221 × log₁₀(height)) − 450; BMI = weight / height²

Limits of the method

The error is around ±3–4% against DXA and grows with atypical body shapes. Measure in the morning before eating, with the tape snug but not tight, at the same landmarks each time: a 1 cm difference at the waist noticeably shifts the result. BMI does not distinguish muscle from fat and does not apply to athletes, pregnancy or children.

Sources of the method

This calculation is for reference only and is not medical advice, a diagnosis or a prescription. If you have a medical condition, are pregnant, take medication or have any doubts, discuss the result with a physician or a qualified nutrition professional.

How to measure body fat using the US Navy Method

Grab a flexible tape measure

Use a standard measuring tape snug against the skin without compressing soft tissue. Measure in the morning.

Take required circumferences

Men need neck and waist. Women need neck, waist, and hips. Keep the tape parallel to the floor.

Review your body composition

View your estimated body fat percentage, total fat mass, and lean muscle mass.

Real-world body composition examples

Athletic standard12.5% body fat

Male, 178 cm (5'10"), 76 kg (167 lb)

Fat mass: 9.5 kg (20.9 lb). Lean body mass: 66.5 kg (146.6 lb). Visible abdominal definition and high insulin sensitivity.

Category: Athletic (Athletes).

Fitness standard22.0% body fat

Female, 168 cm (5'6"), 61 kg (134 lb)

Fat mass: 13.4 kg (29.5 lb). Lean mass: 47.6 kg (104.9 lb). Healthy body fat supporting optimal hormonal and reproductive health.

Category: Fitness.

Fat reduction target28.4% body fat

Male, 175 cm (5'9"), 88 kg (194 lb)

Fat mass: 25.0 kg (55.1 lb). Lean mass: 63.0 kg (138.9 lb). Recommended gradual fat loss of 8–10 kg while preserving lean tissue.

Category: Overweight / Average.

Body Fat Percentage Standards (ACE & WHO)

Category	Men	Women	Physiological Profile
Below the physiological minimum	2–5%	10–13%	Minimum essential fat required for organ protection and nervous system function
Athletic range	6–13%	14–20%	Competitive athletes, maximum vascularity and muscular separation
Fitness range	14–17%	21–24%	Lean athletic build with clear muscle tone and excellent metabolic health
Average range	18–24%	25–31%	Typical population average with moderate health parameters
Obesity range	≥ 25%	≥ 32%	Elevated risk of insulin resistance, cardiovascular disease, and metabolic syndrome

The US Navy circumference equation (Hodgdon & Beckett)

Developed in 1984 by the Naval Health Research Center across thousands of service personnel, calibrated against hydrostatic underwater weighing. The error margin is within 3–4%, rivaling DEXA scans without any specialized equipment.

Fat mass vs Lean mass: Why bathroom scales deceive you

Standard scales only measure total mass. When strength training and dieting, you may lose body fat while gaining muscle tissue—the scale remains flat, but your physique and body fat percentage improve dramatically.

Frequently asked questions

How accurate is the US Navy method?

It correlates with hydrostatic weighing and DEXA scans at r = 0.85–0.90 with an error margin of ±3–4%, outperforming cheap consumer bioimpedance scales that fluctuate with water levels.

Why do women require a higher body fat percentage?

Essential fat for women is 10–13% (compared to 2–5% in men) to maintain estrogen synthesis, regular menstrual cycles, and reproductive health.

How often should I measure body fat?

Every 2 to 4 weeks under identical conditions (morning, fasted). Daily measurements capture meaningless water retention rather than actual tissue changes.

Can you spot-reduce belly fat?

No. Fat mobilization occurs systemically via lipolytic hormones. Abdominal exercises strengthen core musculature but do not selectively burn overlying visceral or subcutaneous fat.

What is a healthy body fat goal for longevity?

12–18% for adult men and 20–25% for adult women provides optimal cardiovascular, hormonal, and metabolic longevity.

Calculate calorie and protein requirements based on your lean mass:

Daily calorie needs calculator (TDEE) →Macronutrient calculator →Water intake calculator →

Other calculators

Fitness and exercise physiology

What next

Formula breakdowns, biomarker reference ranges and nutrition articles with cited sources are in the NutriFit knowledge base.

Go to the knowledge base