Body Fat Calculator
What percentage of your body is actually fat?
About Body Fat Calculator
Body fat percentage is the proportion of your total body weight made up of fat tissue. The US Navy method — developed and validated by Hodgdon & Beckett at the Naval Health Research Center — estimates this from simple circumference measurements using a tape measure, with an accuracy of approximately ±3.5%. Results are classified using the American Council on Exercise (ACE) standard, the most widely used clinical body fat classification in fitness and healthcare.
Male: 495 ÷ (1.0324 − 0.19077×log(waist−neck) + 0.15456×log(height)) − 450 Female: 495 ÷ (1.29579 − 0.35004×log(waist+hip−neck) + 0.22100×log(height)) − 450 (All measurements in cm · Hodgdon & Beckett, 1984)
Source: Hodgdon & Beckett, 1984 — Naval Health Research Center · ACE Body Fat Classification (American Council on Exercise) · Siri WE, 1956 — Body Composition from Fluid Spaces and Density
Why Your Body Fat Result Matters
Body fat percentage reveals what weight and BMI cannot — the actual ratio of fat to lean mass in your body. Research consistently links excess body fat, particularly visceral fat around internal organs, to serious health conditions. Your result is a direct signal worth acting on.
Cardiovascular & Metabolic Risk
Excess visceral fat releases inflammatory cytokines that raise LDL cholesterol, lower HDL, and drive insulin resistance — the root of cardiovascular disease, type 2 diabetes, and metabolic syndrome. Reducing body fat is one of the most evidence-backed ways to lower all three risks simultaneously.
Hormonal Balance
Body fat directly influences estrogen, testosterone, and cortisol production. Excess fat disrupts hormone regulation in both men and women; equally, too little fat (below essential levels) causes hormonal shutdown, amenorrhea, and impaired organ function. Your result shows whether you are in a healthy hormonal range.
The Measure BMI Cannot Give You
BMI cannot distinguish a kilogram of muscle from a kilogram of fat. A trained athlete may register as 'overweight' on BMI while having excellent body fat levels. Body fat percentage gives you the accurate picture — whether you are genuinely overfat, underfat, or at optimal composition.
How to Use Body Fat Most Effectively
The Navy method is a practical, accessible estimate — not a clinical measurement. Understanding its limitations helps you get the most accurate readings and interpret your results correctly:
Measure correctly and consistently — technique is everything
A 1 cm error in waist or hip measurement can shift your result by 1–2%. Always measure at the same time of day (morning, before eating), use the same tape, and take 2–3 readings averaged together. Consistent technique matters more than any single number.
Navy method is an estimate — DEXA is the clinical gold standard
The formula carries an accuracy of approximately ±3.5% compared to DEXA (Dual-Energy X-ray Absorptiometry), the gold standard for body composition. Use your result for tracking trends and general guidance. For clinical-grade precision — such as pre-surgery assessment or elite athletic planning — seek DEXA or hydrostatic weighing.
Healthy ranges shift with age — don't use a single benchmark
Body fat naturally increases with age as muscle mass (sarcopenia) declines. A 45-year-old with 22% body fat is in a different health context than a 25-year-old at the same percentage. Track your result relative to your age group, and prioritise the direction of change over hitting a fixed number.