BodyFatLab

Body Fat Calculator

A free body fat calculator that produces a screening estimate, not a clinical measurement. Neither method here measures fat directly: the U.S. Navy circumference method infers body fat percentage from height, neck, and waist tape measurements (plus hip for women), and the BMI-based view applies the Deurenberg equation to weight, height, age, and sex. Both carry known error bands — the Navy method typically lands within ±3–4 percentage points of a DEXA scan — so treat the number as a starting point and consult a healthcare professional before making any health, diet, or training decision based on it. The calculator places the estimate in the American Council on Exercise (ACE) category bands so the percentage has context. A 70-inch man with a 15-inch neck and 34-inch waist screens at 17.5% body fat by the Navy method, while the same man at 170 pounds and age 30 screens at 20.0% by the BMI-based estimate — a gap that size between methods is normal, which is exactly why both are framed as estimates. Everything computes in your browser and nothing you enter is uploaded or stored.