Body Fat Calculator

Body fat percentage is the proportion of your total body weight that comes from fat tissue (as opposed to muscle, bone, organs, and water). It's a more direct measure of body composition than BMI, which only compares weight to height. A 200-lb athlete at 12% body fat and a 200-lb sedentary person at 30% have very different bodies despite identical BMI.

The US Navy circumference method is a tape-measure estimate developed in 1984 to screen sailors. It correlates reasonably well with more sophisticated methods (within about 3-4 percentage points of DEXA scans for most people), is free, requires only a tape measure, and is the same method the US military uses for fitness standards. It's less accurate for very lean athletes, very obese individuals, and pregnant women. For competitive-level precision, DEXA scan or hydrostatic weighing remains the gold standard.

Per the American Council on Exercise: men's fitness range is 14 to 17%, women's is 21 to 24%. The 'average' (not unhealthy, just typical for US population) range is 18 to 24% for men and 25 to 31% for women. Essential body fat — the minimum required for organ function and hormonal health — is 2 to 5% in men and 10 to 13% in women. Athletes typically fall in 6 to 13% (men) and 14 to 20% (women). Going below essential fat for extended periods causes hormonal and metabolic disruption.

BMI is a height-weight ratio that doesn't directly measure body composition. Body fat percentage measures composition directly (or estimates it via proxy methods like the Navy tape). For most US adults, the two correlate, but BMI misclassifies athletes (often as overweight despite low body fat) and the elderly (often as normal despite low muscle and high fat). When both are available, body fat percentage is the more informative number for individual health.

Use a fabric tape measure, stand relaxed, and don't compress the skin. Neck: measure just below the larynx (Adam's apple), keeping the tape level. Waist: men measure at the navel level; women measure at the narrowest point of the torso (typically just above the navel). Hip (women only): measure at the widest point of the buttocks, parallel to the floor. Measure twice and average. The US Navy specifies these exact locations — using different spots changes the result.

The Navy formula was developed primarily on a US military population, which skews younger, more male, and more racially mixed than the general population. Research suggests it may slightly over- or underestimate body fat for some ethnic groups (notably populations with different muscle distribution patterns), but the error is generally within 2-3 percentage points. For most US adults, it's a reasonable estimate. If you have access to a DEXA scan or InBody machine, those provide ethnicity-neutral readings.

Essential body fat is the minimum required for normal physiological function — protecting organs, regulating hormones, and providing energy reserves. For men this is roughly 2 to 5% of body weight; for women it's 10 to 13% (higher due to reproductive function). Bodybuilders may briefly drop below these levels for competition, but it's not sustainable. Long-term loss of essential fat causes hormonal disruption (low testosterone in men, amenorrhea in women), impaired immunity, and bone density loss.

Sustainable fat loss tracks at about 0.5 to 1% of body weight per week, or roughly 1 to 2 lb. Going faster typically means losing muscle along with fat, which lowers metabolic rate and makes the loss harder to maintain. A moderate caloric deficit (250 to 750 calories below maintenance), adequate protein (0.7 to 1 g per lb of body weight), and resistance training are the established formula for preserving muscle during a fat-loss phase. Crash diets work short-term but rebound.

Men and women store fat in measurably different patterns — men tend toward visceral (abdominal) storage, women toward subcutaneous (hips, thighs, breasts). The Navy formula reflects this: men's equation uses waist and neck only, while women's adds the hip measurement to capture sex-specific fat distribution. Using the wrong formula will give a substantially incorrect estimate.

Heavily muscular individuals — competitive lifters, bodybuilders, NFL-level athletes — sometimes get inflated body fat readings from the Navy method because the formula doesn't account for unusually thick neck musculature. If your neck circumference is disproportionately large from training, the formula treats some of that muscle as if it were fat. DEXA or hydrostatic weighing is more accurate for highly muscular bodies. For most recreational lifters, the Navy method is still reasonable.