Estimate adult body fat percentage from height and body circumferences with the U.S. military circumference equations, using metric or US measurements.
Body fat percentage estimates the portion of total body mass made up of fat. It differs from BMI, which relates weight to height but does not separate fat, muscle, bone, and other tissues.
This calculator uses circumference equations rather than directly measuring body composition. The result is an estimate and should not be interpreted as a diagnosis or a universal target.
All measurements are inches. Metric entries are converted to inches before this single tested equation is applied.
BF% = 86.010 × log₁₀(waist − neck) − 70.041 × log₁₀(height) + 36.76The equation uses base-10 logarithms, not natural logarithms, with all measurements in inches.
BF% = 163.205 × log₁₀(waist + hips − neck) − 97.684 × log₁₀(height) − 78.387These estimates appear only when optional body weight is supplied.
Fat mass = weight × BF% · Lean mass = weight − fat massMale example: height 70 in, neck 15 in, and waist 35 in gives 86.010×log₁₀(20) − 70.041×log₁₀(70) + 36.76 = 19.429…%, displayed as 19.4%.
Female example: height 65 in, neck 13 in, waist 30 in, and hips 38 in gives 163.205×log₁₀(55) − 97.684×log₁₀(65) − 78.387 = 28.556…%, displayed as 28.6%.
Stand upright without shoes and record vertical height.
Measure consistently around the neck just below the larynx without compressing the skin; keep the tape level or with the slight front-downward position specified by military guidance.
Measure the abdomen horizontally at the navel after a normal relaxed exhale.
Measure the natural waist at its narrowest point and measure the hips horizontally around their widest portion.
The method combines the difference between selected circumferences with height. Separate male and female equations reflect the variables used when the equations were developed. Metric inputs are converted to inches so there is only one formula implementation per sex.
DEXA, hydrostatic weighing, air-displacement plethysmography, skinfold assessment, and clinical evaluation use different techniques and assumptions. Hydration, tape placement, tension, posture, body shape, and rounding can cause results to differ.
BMI is a weight-for-height screening measure and does not distinguish fat mass from lean mass. Circumference equations attempt to estimate body fat, but they also have measurement and population-model limitations. When optional weight is entered, this calculator can show BMI as additional context without treating either value as a diagnosis.
The indicator uses commonly cited American Council on Exercise-style sex-specific bands: essential or very low, athletic, fitness, general, and higher body fat. These broad ranges are descriptive fitness references, not medical classifications or goals.
It is the estimated percentage of total body mass made up of fat tissue.
The calculator applies sex-specific U.S. military circumference equations to height, neck, waist, and, for the female equation, hip measurements.
It is a field estimate. Accuracy depends on the population and measurement technique, and an individual result may differ from laboratory or clinical methods.
For the male equation, measure horizontally at the navel after a relaxed exhale. For the female equation, measure the natural waist at its narrowest point.
The equations were developed with different circumference combinations: waist minus neck for men and waist plus hips minus neck for women.
BMI relates weight to height. Body fat percentage estimates how much body mass is fat. Neither value alone diagnoses health.
Very low body fat can be clinically important, but this estimate is not sufficient to assess health. Seek qualified guidance for personal concerns.
Yes. Body shape and muscularity can make circumference equations or BMI less representative for some athletes.
No. It is intended for adults and does not use age-appropriate pediatric assessment methods.
The methods use different measurements and models. Hydration, device algorithms, body shape, and tape technique can all change results.
Equation, measurement, and body-composition context sources.