The Body Fat Calculator estimates total body fat percentage from simple measurements. The primary result uses the U.S. Navy method (Hodgdon and Beckett, 1984). A secondary estimate uses the BMI method.
Measure to the nearest 0.5 cm (about 1/4 inch) for best results. These formulas are estimates only. More accurate assessment may use bioelectrical impedance, DXA, or hydrostatic weighing.
U.S. Navy method
Measure circumference as follows:
- Waist (men): horizontal level around the navel. Do not pull the stomach in.
- Waist (women): level of the smallest waist width. Do not pull the stomach in.
- Neck: below the larynx, tape sloping slightly downward to the front. Avoid flaring the neck.
- Hip (women only): largest horizontal circumference.
Formulas (U.S. customary, inches)
Men:
Body fat % = 86.010 × log10(waist - neck) - 70.041 × log10(height) + 36.76
Women:
Body fat % = 163.205 × log10(waist + hip - neck) - 97.684 × log10(height) - 78.387
Metric inputs are converted to inches before these equations are applied.
Fat mass and lean mass
Fat mass = body fat % × weight
Lean mass = weight - fat mass
BMI method
First compute BMI from height and weight, then:
- Adult men:
1.20 × BMI + 0.23 × age - 16.2
- Adult women:
1.20 × BMI + 0.23 × age - 5.4
- Boys:
1.51 × BMI - 0.70 × age - 2.2
- Girls:
1.51 × BMI - 0.70 × age + 1.4
American Council on Exercise categories
Jackson & Pollock ideal body fat percentages
Ages between table rows are interpolated. Values outside 20-55 use the nearest table endpoint.
Notes
- Essential fat supports life and reproductive function. Very low body fat should be discussed with a clinician.
- BMI-based body fat can misclassify muscular people. The Navy method uses circumferences and is often preferred for tracking change.
- This tool does not diagnose overweight, obesity, or related conditions.
