Body Fat Calculator
Estimate body fat percentage with the U.S. Navy circumference method. Men enter height, neck, and abdomen; women enter height, neck, natural waist, and hips. Weight is used to estimate fat and lean mass.
Body Fat Calculator tool
About the Body Fat Calculator
Choose inches or centimeters and compare the estimate with descriptive ACE categories. Results are estimates and not medical advice; tape-based estimates are not a substitute for clinical assessment.
How Is Body Fat Calculated?
The equations below describe the calculation. Use the units specified in each expression; results are rounded for display.
Male body fat % = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76
Female body fat % = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387
Fat mass = weight × body fat % / 100; lean mass = weight − fat mass
Example
With male height 70 in, neck 15 in, and abdomen 34 in, the estimate is 17.5%. At 80 kg, fat mass is 14.0 kg and lean mass is 66.0 kg.
How to Use the Body Fat Calculator
- Choose US customary or metric units.
- Enter your height; in US units, use whole feet and remaining inches from 0 to less than 12.
- Select sex and enter neck and waist measurements; add hips for the female equation.
- Enter weight to calculate fat and lean mass.
- Read the live result and calculation breakdown; correct any validation messages.
- Use Reset to restore the sample values, or copy the result for discussion with a clinician.
Body Fat Calculator Examples
Male circumference example
At 70 in tall, neck 15 in, abdomen 34 in, and 80 kg, estimated body fat is 17.5%, in the ACE fitness category.
Female circumference example
At 65 in tall, neck 13 in, waist 28 in, hips 38 in, and 60 kg, estimated body fat is 25.9%, with 15.6 kg fat and 44.4 kg lean mass.
Measurement consistency
Repeat measurements under similar conditions. Tape position and tension can materially change the result.
Category limitations
ACE categories are descriptive references, not diagnoses or universal targets. Very low estimates are not a recommendation to reduce body fat further.
Frequently Asked Questions
Does the formula use natural logarithms?
No. It uses base-10 logarithms and inch measurements. Centimeters are converted to inches before calculation.
Where should I measure?
Measure neck just below the larynx. Men measure the abdomen at the navel; women measure the natural waist and widest hips. Keep the tape level and avoid compressing skin.
Why can the result be invalid?
The logarithm requires a positive circumference difference. Inconsistent measurements can also produce a percentage outside the possible 0–100% range.
What are the ACE ranges?
For men: essential fat 2–5%, athletes 6–13%, fitness 14–17%, average 18–24%, obesity 25%+. For women: 10–13%, 14–20%, 21–24%, 25–31%, and 32%+, respectively. Continuous cutoffs start at each next category’s lower boundary.
Is lean mass the same as muscle?
No. Lean mass includes muscle, water, organs, bone, and other non-fat tissue.