Body Fat Percentage Calculator
The body fat calculator estimates your body fat percentage using the US Navy circumference method, the same approach used by the US military for fitness assessments. Enter neck, waist, and hip measurements (women only for hip) along with height. Returns body fat percentage, fat mass, lean mass, and health category. Metric and imperial.
How to use Body Fat Percentage Calculator
- Select your sex (male or female) as the formula differs by sex.
- Enter your height, neck, and waist measurements.
- Women also enter hip measurement.
- The body fat percentage calculates instantly using the US Navy method.
- Check your result against the fitness category reference table.
Body fat calculator online: the US Navy circumference method
The US Navy body fat method uses a logarithmic formula that correlates circumference measurements with body fat percentage. For men, the formula uses neck circumference, waist circumference, and height. For women, it adds hip circumference. The body fat calculator online applies the following formulas: for men, body fat % = 86.010 × log₁₀(waist − neck) − 70.041 × log₁₀(height) + 36.76. For women, body fat % = 163.205 × log₁₀(waist + hip − neck) − 97.684 × log₁₀(height) − 78.387.
Taking measurements correctly is essential for accurate results. Use a soft measuring tape. Measure the waist at the narrowest point (typically at or just above the navel for the circumference method, not at the hip-bone level used for clothing sizing). Measure the neck just below the larynx (Adam's apple). Women measure the hip at the widest point. Take each measurement twice and use the average. The circumference method for how to measure body fat at home requires only a measuring tape and is significantly more accessible than skinfold calipers or DEXA scanning.
Navy body fat calculator: healthy body fat percentage ranges
A healthy body fat percentage for men is generally 10 to 20 percent. Athletes typically maintain 6 to 13 percent. The fit range is 14 to 17 percent. Acceptable is 18 to 24 percent. Obese is 25 percent and above. For women, essential fat is 10 to 13 percent, athletic is 14 to 20 percent, fit is 21 to 24 percent, acceptable is 25 to 31 percent, and obese is 32 percent and above. Women carry more essential fat due to hormonal and reproductive biological requirements, these are healthy sex differences, not excess fat.
Body fat for women and body fat for men differ significantly at the same BMI level because BMI does not distinguish fat from muscle. Two people with a BMI of 25 could have body fat percentages ranging from 15 to 35 percent depending on their muscle mass and fat distribution. The circumference method provides a more body-composition-specific measurement than BMI and is useful for tracking changes in fat mass and lean mass over time as a training or diet program progresses.
Frequently asked questions
The US Navy method uses circumference measurements and height in a logarithmic formula to estimate body fat percentage. For men, it uses neck, waist, and height. For women, it adds hip measurement. The formula was developed through correlation studies with underwater weighing (hydrostatic weighing), which is considered a gold-standard measurement. The Navy method is a validated and widely used alternative to more expensive or invasive body fat measurement techniques.
Men need three measurements: height, neck circumference (measured just below the Adam's apple), and waist circumference (measured at the narrowest point, typically at or just above the navel). Women need one additional measurement: hip circumference (measured at the widest point). Use a flexible measuring tape and take each measurement twice, using the average. Inconsistent measurement technique is the main source of error in circumference-based body fat estimates.
For men: essential fat is 2–5%, athletic range is 6–13%, fit range is 14–17%, acceptable is 18–24%, and obese is 25% and above. For women: essential fat is 10–13%, athletic is 14–20%, fit is 21–24%, acceptable is 25–31%, and obese is 32% and above. Women require significantly more essential fat than men due to hormonal functions. These ranges are from the American Council on Exercise (ACE) body fat classification system.
The US Navy circumference method has a margin of error of approximately 3 to 4 percentage points compared to DEXA scanning (the clinical gold standard). Hydrostatic weighing and air displacement plethysmography (Bod Pod) are more accurate but require specialized equipment. Bioelectrical impedance analysis (BIA), used in consumer smart scales, has similar or greater error margins to the circumference method and is highly sensitive to hydration levels. For tracking trends over time, the circumference method provides reliable, consistent results if measurement technique is kept consistent.