Body Fat Percentage Calculator
Estimate body fat using the US Navy tape method or your BMI. Shows fat mass, lean mass, and what your number means.
Body fat estimate
Why body fat percentage matters more than weight
Body weight measures total mass — bone, organs, water, muscle, and fat lumped together. Body fat percentage isolates the fat-mass component, which is what most health and aesthetic concerns actually relate to. Two people at the same weight can have radically different body composition: one might be 12% fat and 88% lean (muscular), another might be 30% fat and 70% lean (sedentary).
For training purposes, body fat % is the more useful metric. Weight can plateau or even rise during a period of muscle gain combined with fat loss — body fat % shows the real composition change.
Methods compared (gold to rough)
- DEXA scan — gold standard. Uses low-dose X-rays to image bone, fat, and lean tissue separately. Accurate to within ±1%. Cost: $50–150 per scan in most US cities. Worth it if you want a true baseline.
- Hydrostatic weighing — underwater weighing. Very accurate (±1–2%). Less common because of equipment requirements.
- BodPod — air displacement plethysmography. Similar accuracy to hydrostatic. Available at some universities and specialty labs.
- US Navy tape method (this calculator's default) — uses circumference measurements. ±3–4% vs DEXA. Free, repeatable at home.
- BMI-based estimate (Deurenberg) — uses BMI + age + sex. ±5–8%. Useful when you can't take measurements but inaccurate for athletes.
- Bioelectrical impedance (smart scales, handheld devices) — sends a small current through the body. ±5–10%, highly variable based on hydration. Use the trend, not absolute numbers.
- Skinfold calipers — pinch-the-fat method. ±3–5% with experienced practitioner. Untrained users can be off by 8–10%.
- Visual estimation — comparing to body-fat photo charts. Surprisingly close for trained eyes, ±5%.
US Navy method: how it works
Developed by the US Department of Defense for fitness assessments. It uses circumferences at points where fat tends to concentrate, calibrated against more accurate methods.
For men: BF% = 86.010 × log₁₀(waist − neck) − 70.041 × log₁₀(height) + 36.76
For women: BF% = 163.205 × log₁₀(waist + hip − neck) − 97.684 × log₁₀(height) − 78.387
All measurements in centimeters. The calculator handles unit conversion automatically.
Body fat categories (American Council on Exercise)
ACE's widely-cited categories:
- Men: Essential fat 2–5%, Athletes 6–13%, Fitness 14–17%, Average 18–24%, Obese 25%+.
- Women: Essential fat 10–13%, Athletes 14–20%, Fitness 21–24%, Average 25–31%, Obese 32%+.
Women have higher essential fat because of breast tissue, reproductive system fat, and other sex-specific stores. The categories above already account for this — the “Athletes” range for women isn't comparable to the male range.
How body fat changes with training
Sustainable fat loss for trained individuals: 0.5–1% body fat per month. That sounds slow, but it adds up — going from 25% to 15% takes roughly 10–20 months of consistent dieting and training. Faster loss usually drops more muscle than fat, making the rebound worse.
Targets often quoted in fitness culture:
- Men, “abs visible”: ~12% body fat or below.
- Men, “shredded” (bodybuilding stage): 5–8%. Not sustainable long-term.
- Women, “abs visible”: ~18% body fat or below.
- Women, “shredded”: 10–14%. Often disrupts menstrual cycle if held long-term.
What body fat percentage misses
Two people at the same body fat % can have very different metabolic profiles based on where the fat is stored. Visceral fat (around organs) drives most metabolic disease risk; subcutaneous fat (under skin) is mostly cosmetic. Waist circumference and waist-to-height ratio are simple complementary measures: a waist under half your height is generally protective regardless of BMI or body fat %.
Use this calculator to track trends, not as a final verdict on health. Pair with our BMI Calculator, TDEE Calculator for daily calories, and Macro Calculator for protein targets.