Body Fat Calculator
Estimate body fat percentage using the US Navy circumference method.
TL;DR — Body Fat Calculator: A body fat calculator estimates the proportion of your body weight that is fat tissue, as opposed to muscle, bone and water. Cal44 uses the US Navy circumference method — accurate to within about ±3.5% body fat when measurements are taken correctly, and requires only a flexible tape measure.
What is the Body Fat Calculator?
A body fat calculator estimates the proportion of your body weight that is fat tissue, as opposed to muscle, bone and water. Cal44 uses the US Navy circumference method — accurate to within about ±3.5% body fat when measurements are taken correctly, and requires only a flexible tape measure.
How to use the Body Fat Calculator
- Select your sex (women use an additional hip measurement).
- Measure neck circumference at the narrowest point below the larynx.
- Measure waist at the navel (men) or narrowest point (women).
- Women: measure hips at the widest point.
- Enter height.
- Read estimated body fat percentage and fat-mass / lean-mass breakdown.
Formula
Men: BF% = 86.010 · log10(W − N) − 70.041 · log10(H) + 36.76 Women: BF% = 163.205 · log10(W + Hip − N) − 97.684 · log10(H) − 78.387
W = waist (in) · N = neck (in) · Hip = hip (in) · H = height (in)
Worked example
A man with 36" waist, 16" neck and 70" height: BF% ≈ 86.010 · log10(20) − 70.041 · log10(70) + 36.76 ≈ 17.6%.
Frequently asked questions
What is a healthy body fat percentage?
Common ranges: men 10–20% (athletic 6–13%, fitness 14–17%, average 18–24%, obese 25%+); women 18–28% (athletic 14–20%, fitness 21–24%, average 25–31%, obese 32%+).
How accurate is the US Navy method?
Within about ±3.5% body fat when measurements are precise. Less accurate than DEXA or hydrostatic weighing, but more accurate than skinfold calipers in untrained hands.
Why is BF% better than BMI?
BF% directly measures fat, while BMI only measures weight relative to height. A muscular athlete can have high BMI and low BF%.
How can I lower body fat?
A moderate calorie deficit combined with resistance training preserves muscle while losing fat. Cal44's Calorie Calculator estimates the deficit needed.
How often should I measure?
Once every 2–4 weeks. Daily fluctuations from hydration, food and bowel content will obscure real trends.