Body Fat Calculator
Adjust the inputs below. Results update as you type.
How it works
The U.S. Navy method uses waist, neck, and (for women) hip measurements: body fat % = 86.010 × log₁₀(abdomen − neck) − 70.041 × log₁₀(height) + 36.76 for men. Results are estimates with ±3–4% error. DEXA scan is the gold standard. Healthy ranges: men 6–24%, women 16–30% depending on age and fitness level.
Input guidance
- Use measured values (recent weight, height, activity level) rather than guesses.
- Recalculate every few weeks as your routine and body metrics change.
- Pair screening metrics with context such as sleep, stress, and medical history.
The formula
The US Navy method estimates body fat from tape measurements: for men it uses waist and neck circumference and height; for women it adds the hip measurement, via logarithmic equations.
Worked example
A man with a 36-inch waist, 16-inch neck, and 70-inch height estimates around 18–20% body fat using the Navy formula.
More examples to test
- Maintenance case: keep activity constant and observe expected baseline ranges.
- Adjustment case: change only one major variable to understand sensitivity.
How to interpret results
Use results for awareness and planning, then validate with qualified medical or nutrition professionals for individualized decisions.
When this can be inaccurate
Population formulas cannot account for all biological factors such as medical conditions, medication effects, body composition differences, and genetics.
Sources
- U.S. Navy Body Composition Assessment (NAVADMIN)
- ACE — Body Fat Percentage norms
Change history
- July 2026: Published body-fat estimate path with method accuracy caveats.
Site-wide corrections also appear on the corrections log.
Track body composition and fitness goals
General wellness tracking resource.
Frequently asked questions
How accurate is the tape method?+
The Navy method is reasonably good for tracking changes over time, though it can be off by several points versus DEXA or hydrostatic weighing.
What is a healthy body fat percentage?+
Rough ranges are about 10–20% for men and 18–28% for women, with athletes lower. Essential fat is higher in women for hormonal health.
Why measure body fat, not just weight?+
Body fat percentage distinguishes fat from muscle, giving a clearer health picture than weight or BMI alone.
Can this calculator diagnose a condition?+
No. It is a screening and education tool only, not a clinical diagnosis.
When should I seek professional advice?+
Seek professional advice when results are extreme, persistent, or conflict with symptoms, goals, or prior medical guidance.
Guided next steps
Want the full workflow? Use this calculator inside a step-by-step guide.