Calculate your body fat percentage using the US Navy method. Get an accurate estimate of your body composition based on your measurements.
Body fat percentage is the proportion of your body weight that is fat versus lean mass (muscle, bone, organs). It's a better indicator of health than BMI alone as it distinguishes between fat and muscle.
Men:
Women:
Use a flexible tape measure. For neck: measure around the neck just below the voice box. For waist (men): measure at navel level. For waist (women): measure at the narrowest point. For hips (women): measure at the widest point around the buttocks.
Yes, body fat percentage provides a far more accurate picture of health and fitness than BMI. BMI only considers height and weight, categorizing muscular athletes as overweight or obese despite low body fat. A bodybuilder at 90kg and 180cm has a BMI of 27.8 (overweight) but might have only 8% body fat, making them extremely lean. Conversely, someone with normal BMI of 23 could have 30% body fat if they're sedentary with little muscle mass, putting them at higher health risk than their BMI suggests. Body fat percentage distinguishes between weight from muscle versus fat, which matters enormously for health outcomes. Excess visceral fat around organs increases cardiovascular disease, diabetes, and metabolic syndrome risks regardless of total weight. Two people weighing 75kg can look completely different and have vastly different health profiles depending on whether they're 12% or 28% body fat. The US Navy method used in this calculator isn't as accurate as DEXA scans or hydrostatic weighing but provides reasonable estimates without expensive equipment. For tracking progress, consistency matters more than absolute accuracy — measuring the same way monthly shows whether you're gaining muscle or losing fat even if the exact percentage is slightly off.
Healthy ranges vary significantly by gender due to biological differences. Women require higher essential body fat (10-13%) for reproductive function, hormone regulation, and childbearing, whilst men need only 2-5% essential fat. For men, 10-20% is athletic to fit, 21-24% is average/acceptable, and above 25% indicates obesity. For women, 14-24% covers athletic to fit ranges, 25-31% is average, and 32%+ indicates obesity. However, age affects optimal ranges: younger adults typically carry less body fat, whilst slightly higher percentages in older adults may be acceptable or even beneficial for bone density and hormone production. A 25-year-old man at 18% body fat is fit; at 65 that same percentage is excellent. Very low body fat (under 10% for men, under 18% for women) maintained year-round can disrupt hormones, reduce immune function, and cause fatigue, menstrual irregularities in women, and decreased bone density. Bodybuilders achieve 5-7% for competitions but don't maintain that dangerously low level long-term. Athletes in different sports have different optimal ranges: distance runners often carry 8-15%, whilst rugby players might be 12-18%. Rather than chasing extremely low body fat, aim for a sustainable percentage where you feel energetic, perform well, and maintain healthy hormone levels and immune function.
Reducing body fat while preserving muscle requires combining moderate calorie deficit with strength training and adequate protein. Create a 300-500 calorie daily deficit through diet and activity — more aggressive deficits risk muscle loss and metabolic slowdown. Prioritize protein at 1.6-2.2g per kg bodyweight to preserve lean mass during fat loss; this also increases satiety and has higher thermic effect than carbs or fats. Strength train 3-4 times weekly to signal your body to retain muscle rather than breaking it down for energy. Add moderate cardio for additional calorie burn but don't rely solely on cardio which can promote muscle loss. Focus on whole foods — vegetables, lean proteins, whole grains, healthy fats — rather than processed foods which are calorie-dense but less satiating. Track progress through measurements, photos, and how clothes fit alongside scale weight; you might lose fat and gain muscle simultaneously resulting in minimal weight change but dramatic body composition improvement. Aim for 0.5-1% body fat loss monthly for sustainable results without muscle loss; faster loss usually means you're losing valuable lean tissue. Sleep 7-9 hours and manage stress as cortisol promotes fat storage, particularly visceral abdominal fat. Be patient: healthy fat loss takes months, not weeks, but results last unlike crash diets that rebound quickly.
Measurements: Neck 40cm, Waist 90cm. Using US Navy formula for men: Body fat % = 495 / (1.0324 - 0.19077 × log10(90-40) + 0.15456 × log10(180)) - 450 = approximately 20.5%. This falls in the "average" category for men. For improved fitness, targeting 15-18% through strength training and modest calorie deficit would be realistic over 4-6 months.
Measurements: Neck 33cm, Waist 75cm, Hips 100cm. Using US Navy formula for women: Body fat % = 495 / (1.29579 - 0.35004 × log10(75+100-33) + 0.22100 × log10(165)) - 450 = approximately 28%. This sits in the "average" range for women. Reducing to 24-26% through consistent training and nutrition would represent excellent progress.
Measurements: Neck 38cm, Waist 78cm. Calculation yields approximately 12% body fat, placing him firmly in the "athletic" category. This level is sustainable year-round with consistent training and indicates excellent fitness. Further reduction would require significant effort for marginal aesthetic improvement and might compromise performance.
The US Navy method provides reasonable estimates but has limitations. It underestimates body fat in very muscular individuals and overestimates in elderly people with muscle loss. DEXA scans, hydrostatic weighing, and BodPod testing are more accurate but expensive and less accessible. For home tracking, consistency matters more than absolute accuracy — measure at the same time of day, same hydration state, and same point in menstrual cycle for women. Measure monthly rather than weekly as body fat changes slowly; daily or weekly variations largely reflect water fluctuation. Avoid measuring after unusually salty meals, intense workouts, or during illness as these affect water retention. Pull the tape snug but don't compress tissue; use the same tension each measurement. Consider that body fat distribution matters as much as total percentage: visceral fat around organs is more dangerous than subcutaneous fat under skin, and men tend to store more visceral fat whilst women store more subcutaneous fat. Waist-to-hip ratio provides additional health information beyond body fat percentage alone. Remember that extremely low body fat isn't healthier — essential fat is crucial for hormone production, brain function, vitamin absorption, and temperature regulation. Focus on sustainable habits producing gradual improvement rather than crash dieting to hit arbitrary body fat targets. If menstrual periods become irregular or energy crashes, you may be too lean for your body's needs regardless of what percentage seems "ideal" in fitness magazines.