Body Fat Calculator

• DXA scan — gold standard. X-ray differentiation of fat, lean mass, bone. Accuracy ±1-2%. Costs $50-200 per scan in most countries; available at hospitals and some fitness clinics.
• Underwater (hydrostatic) weighing — old gold standard before DXA. Accurate ±2-3% but requires specialized facilities; almost obsolete.
• BodPod (air displacement plethysmography) — similar to underwater, drier. ±2-3% accuracy.
• Skinfold calipers (Jackson-Pollock) — ±3-5% with a trained technician. ±5-8% self-measured. Cheap and accessible.
• US Navy method (tape measurement) — ±3-5%. Requires only a measuring tape. Used by US military for fitness screening.
• Bioelectrical impedance (BIA) — bathroom scales, fitness trackers. ±5-10%. Hydration-sensitive; same person measured at different times of day differs by 2-3 percentage points.
• BMI-derived — estimate body fat from BMI alone. ±10% or worse. Useful only when no measurement is possible.
• Visual estimation — photos compared to reference charts. Surprisingly accurate (±3-5%) when done by experienced trainers; useless when done by yourself.

• Men: essential (2-5%), athletes (6-13%), fitness (14-17%), acceptable (18-24%), obese (25%+).
• Women: essential (10-13%, higher than men due to reproductive function), athletes (14-20%), fitness (21-24%), acceptable (25-31%), obese (32%+).
• The difference reflects sex-specific body composition — women carry more "essential" fat for reproductive function. A "fit" body fat for a man is "athletic" for a woman.
• Athletes vs fitness — competitive bodybuilders compete at 4-6% (men) / 8-12% (women) on stage but rebound to 8-12% / 15-20% off-season. Sustained ultra-low body fat is unhealthy long-term.

Smart scales claim to measure body fat via bioelectrical impedance — they pass a tiny current through your feet, measure resistance, and estimate composition from resistance models. The problem: water conducts electricity. Hydration status changes resistance by more than body composition changes month-to-month. The same person measured at morning vs evening, fed vs fasted, before vs after exercise can show 3-5% different "body fat" without any actual change.

Use BIA scales for trend over weeks/months at consistent conditions (same time of day, same hydration status). Do not trust single readings.

• You want a baseline body fat estimate before starting a fitness or weight-loss program.
• You are tracking changes during a body-recomposition phase (gaining muscle, losing fat at similar weight).
• You are comparing BMI vs body fat for a friend or family member to explain why "BMI says obese, mirror says fit".
• You want to set realistic targets based on body-fat ranges rather than scale weight.

• It will not give DXA-level accuracy. Tape and BMI methods are ±3-10%; for clinical-grade accuracy, get a DXA scan.
• It will not give medical advice. Body fat outside typical ranges (very low or very high) warrants conversation with a clinician, not a calculator readout.
• It will not measure visceral fat separately. Visceral (around organs) and subcutaneous (under skin) fat have different health implications; only DXA and MRI separate them.