Body Fat Calculator

Body Fat Calculator

Estimate your body fat percentage using the US Navy circumference method locally inside your web browser. Unlike BMI, which only knows your weight and height, this method uses actual body measurements — neck, waist, and hip — to produce a body fat percentage estimate that accounts for body shape differences.

Input Methodology

1. 1Select Gender: Choose male or female (the formula differs significantly between sexes).
2. 2Enter Height: Input height in centimetres.
3. 3Measure Neck Circumference: Measure at the narrowest point of the neck, just below the larynx.
4. 4Measure Waist Circumference: For men, measure at the navel. For women, measure at the narrowest point of the waist.
5. 5Measure Hip Circumference (Females Only): Measure at the widest point of the hips and buttocks.
6. 6Review Results: See body fat percentage and fitness category.

Body Fat Calculator — US Navy Circumference Method

This utility estimates body fat percentage using the US Navy circumference method, the standard used by the US Military for body composition assessment. It takes gender, height, neck circumference, waist circumference, and (for females) hip circumference, applies a validated logarithmic formula, and outputs a body fat percentage estimate alongside a fitness category classification.

• Body Fat Percentage Seems Too High: Verify that all measurements are in centimetres (not inches). Re-measure waist at the correct anatomical landmark.
• Female Result Missing Hip Input: The hip measurement field only applies to female calculations. Verify your gender selection is correct.
• Result Changes Each Session: The tool does not save measurement data. Re-enter your measurements each time.

How accurate is the US Navy circumference method?

Research studies comparing the Navy method to DEXA scanning show a mean error of approximately ±3–4% body fat. This means an individual measured at 20% BF could have a true value between 16–24%. Use it to track trends, not as an absolute clinical measurement.

Why does the female formula include hip circumference but the male formula does not?

Women typically store more fat in the gluteal-femoral region (hips and thighs) rather than the abdominal region. The hip circumference captures this fat distribution pattern, improving accuracy for female body fat estimation.

What is essential body fat?

Essential fat is the minimum body fat required for basic physiological function: protecting organs, hormone production, and nerve insulation. Men need approximately 2–5% and women 10–13%. Dropping below essential fat levels is medically dangerous.

Is my measurement data stored anywhere?

No. All calculations run client-side in your local browser.

• BMI Calculator: Calculate your Body Mass Index (BMI) instantly based on weight and height.
• Calorie Calculator: Determine daily calorie targets for weight maintenance, loss, or gain.
• BMR Calculator: Determine your Basal Metabolic Rate (BMR) using Mifflin-St Jeor formula.
• Water Intake Calculator: Calculate standard daily hydration requirements relative to weight and exercise load.
• Ideal Weight Calculator: Determine estimated ideal body weights based on Devine and Robinson equations.
• Protein Intake Calculator: Calculate standard daily protein guidelines for body composition goals.

Result Interpretation Guidance

• Male, 30 years: Height 180 cm, Neck 38 cm, Waist 90 cm.

BF% = 86.010 × log₁₀(90−38) − 70.041 × log₁₀(180) + 36.76

= 86.010 × 1.716 − 70.041 × 2.255 + 36.76 ≈ 18.4% (Average category).

• Female, 28 years: Height 165 cm, Neck 33 cm, Waist 75 cm, Hip 95 cm.

BF% = 163.205 × log₁₀(75+95−33) − 97.684 × log₁₀(165) − 78.387

= 163.205 × 2.212 − 97.684 × 2.217 − 78.387 ≈ 25.1% (Average category).

• Fitness Enthusiasts: Tracking body fat changes over time rather than relying solely on weight, which conflates fat loss and muscle gain.
• Athletes in Weight-Class Sports: Monitoring body composition to ensure weight class is met through fat reduction rather than dehydration.
• Personal Trainers: Providing clients with a measurement-based body composition assessment using only a measuring tape.
• Individuals Who Feel BMI Misrepresents Their Fitness: Athletes and muscular individuals whose BMI shows overweight despite low body fat.

• Establishing a baseline body fat percentage before starting a cutting or body recomposition program.
• Tracking body composition changes every 4–8 weeks during a structured diet and training phase.
• When you want a body fat estimate without access to DEXA scanners, hydrostatic weighing, or BIA scales.

• Do not use circumference methods for clinical body composition assessment. DEXA (dual-energy X-ray absorptiometry) remains the clinical gold standard.
• Do not measure immediately after exercise. Post-workout swelling and fluid redistribution temporarily affect circumference measurements, producing inconsistent results.
• Pregnant women: Circumference measurements during pregnancy do not reflect fat distribution and will produce meaningless body fat estimates.

Regulatory & Professional Disclaimer