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Body Fat Calculator

Estimate body fat percentage using the US Navy method and BMI method. Shows fat mass, lean mass, ideal body fat, and ACE categories.

Measure at the widest point. All measurements in cm. Age and weight needed for BMI method.

Category Male Female
Essential fat 2–5% 10–13%
Athletes 6–13% 14–20%
Fitness 14–17% 21–24%
Average 18–24% 25–31%
Obese ≥25% ≥32%

Results are estimates. Professional assessment (DEXA, hydrostatic weighing) is more accurate.

What is Body Fat Calculator?

The Body Fat Calculator estimates your body fat percentage using two methods: the US Navy circumference method (based on height, neck, waist, and hips) and the BMI method (based on BMI and age). It shows both results side by side, along with your fat mass, lean body mass, ideal body fat percentage by age bracket (Jackson & Pollock), estimated fat to lose to reach ideal, and your ACE fitness category.

How to use

  1. 1 Select your biological sex.
  2. 2 Enter your age and weight (needed for BMI method and mass calculations).
  3. 3 Enter height, neck, and waist measurements in cm.
  4. 4 For females, also enter hip circumference.
  5. 5 Both Navy and BMI method results appear side by side.
  6. 6 Review your fat mass, lean mass, ideal body fat, and ACE category.

Formula

Navy (male): BF% = 495 / (1.0324 − 0.19077×log10(waist−neck) + 0.15456×log10(height)) − 450. BMI method (male): BF% = (1.20×BMI) + (0.23×age) − 16.2. BMI method (female): BF% = (1.20×BMI) + (0.23×age) − 5.4.

Example calculation

A 35-year-old male, 175 cm, 80 kg, neck 38 cm, waist 90 cm: Navy BF% ≈ 22%, BMI method BF% ≈ 22.5%. Fat mass ≈ 17.6–18.0 kg, lean mass ≈ 62–62.4 kg. Ideal BF% for age 35 ≈ 18–22% (fitness range). Fat to lose to reach ideal ≈ 0–4 kg.

Frequently asked questions

How accurate is the US Navy method?

The Navy method has an error margin of roughly ±3–4 percentage points compared to DEXA scanning. It is a reliable screening tool but not a clinical-grade measurement.

What is the BMI method for body fat?

The BMI-based formula (Deurenberg et al.) estimates body fat from BMI and age. It is less accurate than circumference methods but useful when you only have a scale and height — no tape measure needed.

What is a healthy body fat percentage?

ACE guidelines: for males, essential fat is 2–5%, athletes 6–13%, fitness 14–17%, average 18–24%, obese ≥25%. For females: essential 10–13%, athletes 14–20%, fitness 21–24%, average 25–31%, obese ≥32%.

What is lean body mass?

Lean body mass (LBM) is everything in your body except fat — muscle, bone, organs, water, and connective tissue. Total weight − fat mass = LBM. LBM is used in drug dosing, BMR calculation, and fitness tracking.

How is body fat different from BMI?

BMI uses only height and weight and cannot distinguish muscle from fat. Body fat percentage directly measures the proportion of fat tissue, making it a more meaningful health indicator, especially for muscular individuals.