Body Fat Calculator
Estimate body fat percentage
Formula
US Navy Method:
Men: 86.01×log10(waist-neck) - 70.04×log10(height) + 36.76
Women: 163.2×log10(waist+hip-neck) - 97.68×log10(height) - 78.39
Healthy Ranges
| Category | Men | Women |
|---|---|---|
| Essential | 2-5% | 10-13% |
| Athletic | 6-13% | 14-20% |
| Fitness | 14-17% | 21-24% |
| Average | 18-24% | 25-31% |
| Obese | 25%+ | 32%+ |
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Complete Guide to Body Fat Calculator
Body fat percentage is a more accurate indicator of health and fitness than weight alone. It measures the proportion of your body that is fat versus lean mass (muscle, bone, organs, water). Two people at the same weight can look completely different based on their body composition.
Understanding the US Navy Method
This calculator uses the US Navy circumference method, developed by Hodgdon and Beckett in 1984. It's accurate within 3-4% for most people, making it one of the most reliable at-home measurement methods. The Navy uses it to assess fitness of service members.
How to Measure Correctly
- Waist: Men: at navel level. Women: at narrowest point (usually above navel). Keep tape horizontal, don't suck in.
- Neck: Just below the larynx (Adam's apple), tape sloping slightly downward in front.
- Hips (women only): At the widest point of your buttocks.
- Take 3 measurements each and average them for accuracy.
Why Body Fat Matters More Than Weight
Body fat percentage tells you about body composition. Someone with 25% body fat has more fat than muscle compared to someone at 15%. High body fat (especially visceral/belly fat) is linked to heart disease, diabetes, and metabolic syndrome, regardless of weight.
Healthy Body Fat Ranges
Ranges differ by sex because women naturally carry more essential fat for hormonal and reproductive functions. Extremely low body fat (below essential levels) can cause hormonal problems, immune dysfunction, and organ damage.
Frequently Asked Questions
The Navy method is accurate within 3-4% for most people. This means if you get 20%, your actual body fat could be 17-23%. It's one of the most reliable at-home methods, though DEXA scans and hydrostatic weighing are more precise.
Essential fat is the minimum fat needed for basic physiological function - hormone production, vitamin absorption, nervous system protection, and organ cushioning. For men it's 2-5%, for women 10-13%. Going below these levels is dangerous.
Women naturally carry more essential fat for hormonal function, breast tissue, and reproductive health. This is biological and healthy. The 'healthy' ranges for women are therefore 8-10 percentage points higher than for men.
Visible abs typically appear at 10-14% for men and 16-20% for women. However, this varies by genetics and how much abdominal muscle you have. More muscle makes abs visible at slightly higher body fat percentages.
Monthly measurements are ideal. More frequent measurements can show misleading fluctuations due to hydration, food intake, and measurement inconsistency. Focus on long-term trends over 3+ months.
No. Extremely low body fat causes hormonal imbalances, weakened immunity, bone loss, and reproductive issues. The 'fitness' range (14-17% men, 21-24% women) is healthy and sustainable for most active people.
Bathroom scales use bioelectrical impedance (BIA) which is affected by hydration, food intake, and time of day. BIA can be off by 8% or more. The Navy method using measurements is generally more consistent.
No, spot reduction is a myth. You can't choose where fat comes off. Fat loss occurs systemically. However, you can build muscle in specific areas to improve appearance as overall body fat decreases.