Advanced Body Fat Calculator

Body fat percentage is the proportion of your total body weight that is fat tissue. It includes essential fat (needed for organ function, ~2-5% in men, ~10-13% in women) and storage fat (energy reserves). Unlike BMI, body fat % distinguishes between muscle and fat—a muscular athlete and an obese person can have the same BMI but vastly different body fat percentages.

The US Navy Method uses circumference measurements (neck, waist, and hip for women) with height to estimate body fat. Developed for military fitness assessments, it correlates well with DEXA scans (±1-3% accuracy). Men: 495/(1.0324-0.19077×log(waist-neck)+0.15456×log(height))-450. Women add hip measurement to the formula.

The Deurenberg formula estimates body fat from BMI, age, and gender. It's convenient (only needs height/weight) but less accurate than tape methods—typically ±4-5% from DEXA. It overestimates for muscular individuals and underestimates for elderly with sarcopenia (muscle loss). Best for general population screening, not athletes.

RFM is a newer formula (2018) using only height and waist circumference. Research shows it correlates as well as DEXA for estimating body fat. Men: 64-(20×(height/waist)). Women: 76-(20×(height/waist)). It's simpler than Navy method (no neck measurement) and more accurate than BMI-based estimates.

For men by category: Essential fat: 2-5% (minimum for survival). Athletes: 6-13% (competition-ready). Fitness: 14-17% (visible abs, lean). Average: 18-24% (healthy but not lean). Obese: 25%+. Ideal ranges vary by age—a 25-year-old should aim for 11-14%, while a 50-year-old might aim for 16-20%.

For women by category: Essential fat: 10-13% (minimum for hormonal function). Athletes: 14-20% (competition-ready). Fitness: 21-24% (toned appearance). Average: 25-31% (healthy but not lean). Obese: 32%+. Women need more essential fat than men for reproductive health.

FFMI measures lean (fat-free) mass relative to height: FFMI = Lean Mass (kg) / Height (m)². It assesses muscularity independent of fat. Men: 18-20 average, 22+ fit, 25+ exceptional (often indicates steroid use above ~25). Women: 15-17 average, 19+ fit. More useful than BMI for athletes and bodybuilders.

Women require 10-13% essential fat (vs 2-5% for men) due to biological differences: fat in breasts, hips, and thighs supports reproductive function, estrogen production, and pregnancy. Below essential levels, women may experience amenorrhea (loss of menstruation), bone loss, and hormonal dysfunction.

Measurement tips: Measure in the morning, after using the bathroom, before eating. Waist: at navel level (not narrowest point), exhale normally. Neck: below Adam's apple, tape level. Hip (women): widest point of buttocks. Use a flexible tape, keep it snug (not tight), and take 2-3 measurements to average.

Gold standard methods: DEXA scan (±1-2%), hydrostatic weighing (±2-3%), Bod Pod (±2-3%). Our calculator methods: US Navy (±1-3%), RFM (±3%), BMI-based (±4-5%). The Navy method is most accurate of home methods when measurements are taken correctly. For tracking trends, consistency matters more than absolute accuracy.

Yes! 'Skinny fat' (metabolically obese normal weight) means having normal BMI but high body fat and low muscle mass. You might be 22 BMI but 30% body fat. This is why body fat % is more informative than weight alone. Skinny fat individuals have similar metabolic risks (diabetes, heart disease) as visibly overweight people.

Safe fat loss rate: 0.5-1% of body weight per week (0.5-1 kg for most people). Faster loss risks muscle loss, metabolic slowdown, and nutrient deficiencies. At 500-1000 calorie daily deficit, expect 0.5-1 lb fat loss per week. Higher body fat individuals can lose faster initially; leaner individuals should go slower.

Yes, significantly. High body fat (especially visceral fat around organs) increases risk of: Type 2 diabetes, heart disease, certain cancers, sleep apnea, fatty liver, and inflammation. Very low body fat also has risks: hormonal dysfunction, immune suppression, bone loss, and fertility issues. The 'fitness' range balances health and performance.

Fat mass is total body fat (essential + storage). Lean mass (fat-free mass) is everything else: muscle, bone, organs, water, connective tissue. Example: 80kg person at 25% body fat has 20kg fat mass and 60kg lean mass. When losing weight, the goal is to preserve lean mass while reducing fat mass through proper nutrition and resistance training.

Weekly or bi-weekly for tracking trends with the same method, same time of day, same conditions. Don't obsess over daily fluctuations—hydration, food, and time of day affect measurements. Monthly progress photos alongside measurements give a more complete picture. Focus on 4-8 week trends rather than day-to-day changes.