Health

Body Fat Percentage Calculator

Estimate your body fat using the U.S. Navy method or a BMI-based fallback. Free, fast, no sign-up.

Method

U.S. Navy BMI (Deurenberg)

Metric (kg, cm) Imperial (lb, ft/in)

Gender

Male Female

Age

Height (cm)

Weight (kg)

Neck (cm)

Waist (cm)

Body Fat

— %

Fill in the measurements to estimate body fat

Fat mass —

Lean mass —

Method —

What is body fat percentage?

Body fat percentage is the share of your total body mass that is fat tissue, as opposed to lean mass (muscle, bone, organs, water). Unlike BMI, which only looks at weight versus height, body-fat percentage tells you about body composition — and that distinction matters. A muscular person and a sedentary person at the same BMI can have very different fat percentages, with very different health implications. The most accurate measurements come from DEXA scans, hydrostatic weighing, or air-displacement plethysmography (Bod Pod), but those need a lab. For at-home estimates, two methods stand out: the U.S. Navy circumference method, which uses tape measurements at the neck, waist (and hips for women) plus your height, and the Deurenberg BMI formula, which only needs height, weight, age and sex. Both produce useful ballpark numbers — typically within 3-4 percentage points of a DEXA — when measurements are taken consistently. Use this as a tracking tool, not a diagnostic one. This calculator is for informational purposes only and does not replace medical advice.

How to use this calculator

1. Pick the U.S. Navy method (more accurate) or BMI fallback. 2. Choose metric or imperial units and your gender. 3. For the Navy method, measure your neck just under the larynx, your waist at the narrowest point above the navel (men) or at the navel level (women), and — if female — your hips at the widest point. Keep the tape level and snug, not tight. Take each measurement twice and use the average. 4. Enter your height, weight and age. The result, ACE category, fat mass and lean mass appear automatically.

How body fat is calculated

The U.S. Navy method uses logarithmic regressions on circumference measurements (in inches): Men: BF% = 86.010 × log₁₀(waist − neck) − 70.041 × log₁₀(height) + 36.76 Women: BF% = 163.205 × log₁₀(waist + hip − neck) − 97.684 × log₁₀(height) − 78.387 The Deurenberg formula (BMI fallback) is: BF% = 1.20 × BMI + 0.23 × age − 10.8 × sex − 5.4 (sex = 1 for males, 0 for females). From the result, fat mass = weight × BF% / 100, and lean mass = weight − fat mass.

ACE body fat categories

The American Council on Exercise (ACE) classifies body fat into five general categories. Healthy ranges differ between men and women because women carry more essential fat for hormonal and reproductive function.

Category	Men	Women
Essential fat	2 — 5 %	10 — 13 %
Athletes	6 — 13 %	14 — 20 %
Fitness	14 — 17 %	21 — 24 %
Average	18 — 24 %	25 — 31 %
Obese	≥ 25 %	≥ 32 %

Frequently asked questions

How accurate is the U.S. Navy method?

Studies put it within roughly 3-4 percentage points of a DEXA scan when measurements are taken correctly. It tends to overestimate fat in very lean people and underestimate it in those with a lot of abdominal fat. For tracking change over time, consistency matters more than absolute accuracy.

Where exactly should I measure my waist?

For men, measure at the narrowest point of the torso, usually just above the navel. For women, measure at the navel level. Stand relaxed, exhale normally, and keep the tape horizontal. Don't suck in.

Why does the BMI method need age and sex?

Body fat at a given BMI rises with age and is higher in women at the same BMI. The Deurenberg formula adds those terms to correct for both effects. It's less accurate than the Navy method for athletic people but works without a tape measure.

What's a healthy body fat percentage?

Most health authorities consider 14-17% "fitness" range for men and 21-24% for women. Going below essential fat (≈ 5% men, ≈ 13% women) for extended periods can disrupt hormones and immunity. There is no single "perfect" number — context, age, and goals matter.

Can I lower body fat without losing muscle?

Yes. Combine a moderate calorie deficit (10-20% below maintenance) with adequate protein (around 1.6-2.2 g/kg) and resistance training. Sleep and stress management matter too. Lose weight slowly — about 0.5-1% of body weight per week — to preserve lean mass.

Is this calculator a medical diagnosis?

No. It's an estimation tool for general fitness tracking. For clinical decisions, body-composition assessment, or any health concern, consult a doctor, registered dietitian, or sports physician.

Body Fat Percentage Calculator