Body Fat Calculator

Body fat percentage is the proportion of your total body weight that is fat tissue, with the rest being lean mass — muscle, bone, organs, and water. Unlike BMI, which only relates height and weight, body fat percentage tells you what your weight is actually made of. Two people can share the same weight and BMI while having dramatically different body fat percentages and health profiles.

Several measurement methods exist, each with tradeoffs. DXA scans are the clinical gold standard, accurate to within 1–2% but requiring specialized equipment. Hydrostatic weighing is similarly precise but inconvenient. Skinfold calipers measure subcutaneous fat at specific sites and are accurate when performed by a trained operator. Bioelectrical impedance scales are widely available but vary by hydration. The U.S. Navy method — used in this calculator — uses body circumference measurements (height, neck, waist, hip) to estimate body fat with reasonable accuracy in the field.

Healthy body fat ranges differ by gender and age. Athletes typically range 6–13% (men) or 14–20% (women); fitness-level individuals 14–17% or 21–24%; average healthy adults 18–24% or 25–31%; and obese individuals 25%+ or 32%+. Going below the 'essential fat' floor (3% men, 12% women) is medically dangerous and impairs hormonal function, immune response, and recovery.

Body fat percentage is more informative than weight alone for fitness goals. Adding muscle while losing fat can keep weight flat while dramatically improving body composition, fitness markers, and aesthetics. Weight scales miss this transformation entirely. Tracking body fat over time — even with the modest accuracy of field methods — captures real progress that the scale cannot.

For best results with the U.S. Navy method, take measurements consistently: same time of day (morning before eating), same posture (relaxed but standing tall), and same tape tension (snug but not compressing skin). Re-measure every 4–6 weeks rather than weekly, since short-term fluctuations from hydration and digestion can mask genuine progress trends.

How accurate is the U.S. Navy body fat method? It typically falls within ±3–4% of DXA scan results when measurements are taken correctly. This is less accurate than clinical methods but accurate enough for tracking progress over time, especially when you measure the same way each time. The trend matters more than the absolute number.

What's a healthy body fat percentage to target? It depends on your goals. For general health, men should stay under 25% and women under 32%. For visible muscle definition, aim for 10–15% (men) or 18–24% (women). For peak athletic performance, athletes often target lower ranges, but going below essential fat thresholds carries health risks.

How fast can I safely lose body fat? Sustainable fat loss runs 0.5–1% of body weight per week, which works out to roughly 0.5–1 percentage point of body fat per month for most people. Faster rates usually mean significant muscle loss alongside fat. Combine a moderate calorie deficit (300–500 below maintenance) with resistance training to preserve muscle while losing fat.

Should I trust my smart-scale's body fat reading? Bioelectrical impedance scales are convenient but vary significantly with hydration status, recent meals, and skin moisture. Use them only for tracking trends in your own readings under consistent conditions — never compare absolute values from a smart scale to a DXA scan or compare yours to someone else's.

What measurements should I track alongside body fat percentage? Pair body fat with waist circumference, weight, and progress photos. Waist circumference is a strong predictor of metabolic health independent of overall body fat. Photos taken under the same lighting every 4–6 weeks reveal compositional changes that numbers alone often miss.