Body Fat Calculator
Last Updated:
Estimate body fat percentage using the scientifically validated US Navy circumference method. Shows your fitness category.
Estimated Body Fat
0%
Uses the US Navy circumference method. Measure at navel level for waist.
📐 Formula
Male: BF% = 86.010×log₁₀(waist−neck) − 70.041×log₁₀(height) + 36.76. Female: BF% = 163.205×log₁₀(waist+hip−neck) − 97.684×log₁₀(height) − 78.387
How to Use the Body Fat Calculator
Take your measurements
Measure waist at the navel (belly button) level — not the narrowest point. Measure neck below the larynx. Women: measure hips at the widest point. Take measurements after exhaling normally; do not suck in.
Enter height and measurements
Input all measurements in the same unit (cm or inches). Measurement consistency matters more than absolute accuracy — measure at the same time of day and in the same position each time.
Select sex
The US Navy formula uses different equations for men and women. Women require the hip measurement because fat distribution patterns differ significantly between sexes.
Track the trend, not the number
Body fat percentage from any field method has a ±3–4% margin of error. The direction of change over weeks matters more than the single reading.
How the US Navy Body Fat Formula Works
The US Navy circumference method was developed as a field-deployable alternative to hydrostatic weighing for military fitness assessments. It uses logarithmic equations based on circumference measurements that correlate well with more precise methods. For men: BF% = 86.010 × log₁₀(waist − neck) − 70.041 × log₁₀(height) + 36.76. For women: BF% = 163.205 × log₁₀(waist + hip − neck) − 97.684 × log₁₀(height) − 78.387.
Validation studies show accuracy within 3–4% of DEXA (dual-energy X-ray absorptiometry) for most individuals. The method is less accurate for very lean or very obese individuals, and for people with atypical fat distribution patterns.
Body Fat Percentage Categories
For men: Essential fat (2–5%) — minimum for organ function; Athletic (6–13%); Fit (14–17%); Average (18–24%); Obese (25%+). For women: Essential fat (10–13%); Athletic (14–20%); Fit (21–24%); Average (25–31%); Obese (32%+). Women's essential fat is higher due to sex-specific fat (breasts, uterus, hips) required for hormonal and reproductive function. This is physiologically normal, not excess fat.
Why Body Fat % Tells More Than BMI
BMI cannot distinguish between muscle and fat — a muscular athlete and an untrained person of the same height and weight get identical BMI scores with very different health profiles. Body fat percentage directly measures the fat-to-lean ratio, making it a more accurate health and fitness marker. A person can be "normal" BMI but carry a high body fat percentage (called "normal-weight obesity" or "skinny fat") — elevated visceral fat with low muscle mass, carrying metabolic risks similar to obese BMI. Conversely, athletes often register as "overweight" or "obese" by BMI despite being exceptionally lean and fit.
More Accurate Methods for Comparison
DEXA scanning (most accessible accurate method, ~$50–150 at imaging centres): measures bone density, lean mass, and fat mass separately with high precision. Hydrostatic (underwater) weighing: gold standard but rarely accessible. Air displacement plethysmography (Bod Pod): comparable accuracy to hydrostatic, more accessible. Bioelectrical impedance (home scales, gym machines): convenient but highly variable based on hydration; useful only for trend tracking. The Navy method in this calculator is more accurate than bioelectrical impedance for most people and requires only a measuring tape.
Sources & Methodology
Calculations are based on the most current publicly available data from authoritative government and industry sources:
Frequently Asked Questions
For men: Athletic (6–13%), Fit (14–17%), Average (18–24%), Above average (25%+). For women: Athletic (14–20%), Fit (21–24%), Average (25–31%), Above average (32%+). Essential fat is 2–5% for men and 10–13% for women.
The US Navy method is accurate to within 3–4% for most people. It's a reliable field test but less precise than DEXA scanning or hydrostatic weighing. Consistent measurement technique is key.
Measure at the navel (belly button) level, not the narrowest point. Keep the measuring tape horizontal, don't suck in your stomach, and measure after exhaling normally.