Body Fat Calculator — US Navy Formula Percentage Estimate

Healthy body fat ranges by sex and age (American College of Sports Medicine): Men — essential fat 3–5%, athletes 6–13%, fitness 14–17%, acceptable 18–24%, obese 25%+. Women — essential fat 12–15%, athletes 16–20%, fitness 21–24%, acceptable 25–31%, obese 32%+. Note: some body fat is essential for hormonal function, organ protection, and nervous system health — going too low (especially for women) has serious health consequences.

From most to least accurate: (1) DEXA scan (±1–2%): gold standard, uses X-ray density differentiation, measures regional composition; (2) Hydrostatic weighing (±2%): underwater weighing, accurate but less accessible; (3) Air displacement plethysmography — Bod Pod (±2–3%); (4) Skinfold calipers (±3–5%) when done by trained technician; (5) US Navy tape measure method (±3–5%); (6) Bioelectrical impedance scales (±5–8%, highly variable). DEXA is now available at many sports medicine clinics for $50–150.

No — spot reduction is a persistent fitness myth. You cannot target fat loss to a specific area by exercising that area. Fat is mobilized systemically in response to overall energy deficit, not locally from the muscles being exercised. Where your body loses fat first is primarily determined by genetics and hormones. Abdominal fat tends to be most metabolically responsive to calorie deficit in many people, but this is genetically determined, not a result of doing more crunches.

For most men, visible abdominal definition begins around 10–12% body fat; a full 6-pack typically requires 8–10%. For women, visible abs typically appear at 16–20% body fat. These ranges vary based on individual fat distribution, muscle development, and genetics. Getting to these percentages requires both low body fat AND developed abdominal muscle — you can have very low body fat with minimal abs if the muscles themselves aren't developed.

The fundamentals: (1) Create a calorie deficit of 250–500 calories/day below TDEE — this produces 0.5–1 lb/week of fat loss; (2) Consume adequate protein (1.6–2.2g/kg) to preserve muscle during the deficit; (3) Maintain resistance training 2–4 days/week to preserve or build muscle simultaneously; (4) Prioritize sleep (7–9 hours) — sleep deprivation increases hunger hormones and reduces fat oxidation; (5) Be patient — sustainable fat loss is 0.5–1% of body weight per week maximum without significant muscle loss.

Body fat percentage is generally more informative for individuals because it directly measures the quantity of fat tissue rather than using weight relative to height as an indirect proxy. BMI is useful at population level for epidemiological research but fails for muscular individuals (overestimates obesity risk) and for sarcopenic individuals (underestimates risk in those with normal BMI but high fat and low muscle). However, BMI is free and instantaneous; body fat % requires measurement tools.