Precision Utility
Body Fat
Calculator
Method
US Navy
Basis
Circumference
Estimate your body fat percentage in seconds using the US Navy circumference method. Enter your height, neck, waist and (for women) hip measurements — the calculator does the rest. You'll see your body fat percentage, category, fat mass and lean mass breakdown. No scales or specialist equipment needed — just a tape measure.
Measurements
Estimated Body Fat
18.6%
Average
Body Composition
Body Fat %
18.6%
Category
Average
Fat Mass
14.5 kg
Lean Mass
63.5 kg
How the body fat calculator works
Start by selecting your sex — the formula differs because men and women store fat in different patterns. Then enter your height in centimetres.
Next, measure your neck circumference just below the larynx (Adam's apple), your waist at the narrowest point, and — if you selected female — your hips at the widest point. Use a flexible tape measure pulled snug against the skin without compressing it.
Hit calculate and the tool applies the US Navy circumference formula. For men: 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76. For women the hip measurement is added to the equation for improved accuracy.
You'll see your estimated body fat percentage, the category it falls into (essential, athlete, fitness, average or obese), plus your fat mass and lean mass in kilograms. The composition bar gives you a visual split at a glance.
What you need to know about body fat
Body fat is divided into two types. Essential fat is the minimum your body needs to function — it protects organs, insulates nerves and regulates hormones. Men need at least 2–5% and women need 10–13%. Storage fat is the energy reserve stored beneath the skin and around organs. Some storage fat is normal and healthy; too much increases health risks.
Healthy ranges differ by sex:
- Men: 6–17% (athlete to fitness), 18–24% (average). Above 25% is classified as obese.
- Women: 14–24% (athlete to fitness), 25–31% (average). Above 32% is classified as obese.
Why body fat percentage matters more than weight alone:
- Two people at the same weight can have very different body compositions — one lean and muscular, one carrying excess fat
- BMI cannot distinguish muscle from fat, so athletes often score "overweight" despite being very lean
- Excess visceral fat (around internal organs) is linked to higher risk of type 2 diabetes, heart disease and certain cancers
- Tracking body fat percentage over time is a better indicator of fitness progress than scale weight
The US Navy method is one of the most practical ways to estimate body fat at home. It's accurate to within 3–4% of hydrostatic weighing for most people, and all you need is a tape measure.
Frequently asked questions
How does the US Navy body fat method work?
The US Navy method estimates body fat percentage from circumference measurements — neck, waist and (for women) hips — combined with height. It uses a logarithmic formula developed by the US Department of Defense and is accurate to within 3–4% of hydrostatic weighing for most people.
What body fat percentage is healthy?
For men, 14–17% is considered the fitness range and 18–24% is average. For women, 21–24% is fitness and 25–31% is average. Essential fat — the minimum needed for normal body function — is 2–5% for men and 10–13% for women.
Is body fat percentage more useful than BMI?
Body fat percentage tells you how much of your weight is fat versus lean tissue, while BMI only compares weight to height. Someone with a lot of muscle can have a high BMI but low body fat. BF% gives a more accurate picture of body composition and health risk.
Where should I measure my waist for this calculator?
Measure your waist at the narrowest point of your torso, usually at or just above the navel. Stand relaxed and breathe out normally — don't suck in your stomach. Use a flexible tape measure pulled snug but not compressing the skin.
Why do women need a hip measurement but men don't?
The US Navy formula accounts for sex-specific fat distribution patterns. Women typically store more fat around the hips and thighs, so the hip measurement improves accuracy. The male formula uses only neck, waist and height because men tend to store fat primarily around the abdomen.
How accurate is the US Navy body fat calculator?
Studies show the US Navy circumference method is accurate to within 3–4% of results from hydrostatic (underwater) weighing. It's more reliable than skinfold callipers for most people and doesn't require any specialist equipment — just a tape measure.