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Body Fat Calculator

Estimate body fat percentage using the U.S. Navy method and BMI-based formula. Get body fat mass, lean mass, and ideal fat range for your age.

ages 15–80
ftin
lbs
ℹUse a flexible tape measure. Height in ft + in; neck, waist, and hip in inches.
in
in

Measure neck just below the larynx · waist at the narrowest point · hip at the widest point (women only)

How to Use This Calculator

  1. Choose your preferred unit system: US Units (lbs/inches), Metric (kg/cm), or Other Units with per-field unit selection.
  2. Enter your age and select your gender.
  3. Enter your height and weight.
  4. Measure and enter your neck circumference (just below the larynx), waist circumference (at the narrowest point), and — for women — hip circumference (at the widest point).
  5. Click Calculate to see your results instantly.

Example (Male, 30 years, US Units)

Height: 5 ft 10 in · Weight: 175 lbs · Neck: 15 in · Waist: 32 in

Result: ≈ 14.8% — Fitness category

What Is Body Fat Percentage?

Body fat percentage is the proportion of your total body weight that consists of fat tissue. Your body contains two categories of fat: essential fat — the minimum amount needed for basic physiological functions such as hormone production, organ protection, and nerve function — and storage fat, which accumulates in adipose tissue and serves as an energy reserve.

Unlike BMI (Body Mass Index), which only considers height and weight, body fat percentage reveals your actual body composition. Two people with the same BMI can have very different amounts of fat versus muscle, making body fat percentage a far more informative metric for health and fitness goals.

How Is Body Fat Calculated?

This calculator uses two methods to estimate body fat percentage:

U.S. Navy Method (Primary)

Developed by the United States Navy, this method uses circumference measurements to estimate body fat. It requires height, neck, waist, and (for women) hip measurements. All measurements are converted to inches internally.

Men:

86.010 × log₁₀(waist − neck)

− 70.041 × log₁₀(height) + 36.76

Women:

163.205 × log₁₀(waist + hip − neck)

− 97.684 × log₁₀(height) − 78.387

BMI Method (Secondary)

The Deurenberg formula derives an approximate body fat percentage from BMI, age, and gender. It is less accurate than the Navy method but requires no circumference measurements.

BMI = weight(kg) / height(m)²

Men:

1.20 × BMI + 0.23 × age − 16.2

Women:

1.20 × BMI + 0.23 × age − 5.4

Body Fat Categories for Men and Women

The American Council on Exercise (ACE) defines the following body fat categories:

Men

CategoryRange
Essential Fat2–5%
Athletes6–13%
Fitness14–17%
Average18–24%
Obese25%+

Women

CategoryRange
Essential Fat10–13%
Athletes14–20%
Fitness21–24%
Average25–31%
Obese32%+

Source: American Council on Exercise (ACE)

What Is a Healthy Body Fat Percentage?

A "healthy" body fat percentage depends on your age, gender, and fitness goals. In general, the Fitness category is considered optimal for most active adults, while the Average category is acceptable for sedentary individuals. Essential fat is the minimum needed for survival — falling below it can impair organ function.

Ages 20–39

Men: 8–19%

Women: 21–32%

Ages 40–59

Men: 11–21%

Women: 23–33%

Ages 60–79

Men: 13–24%

Women: 24–35%

Ideal ranges based on American College of Sports Medicine (ACSM) guidelines.

How Accurate Is the U.S. Navy Method?

The U.S. Navy circumference method has been validated against hydrostatic (underwater) weighing and DEXA scans. Studies show it has a standard error of approximately ±3–4% for most individuals. It tends to be less accurate for very lean athletes and elderly individuals with significant muscle loss.

For clinical-grade accuracy, methods such as DEXA scanning, hydrostatic weighing, or air displacement plethysmography (Bod Pod) are recommended. The Navy method is, however, an excellent free and practical tool for tracking trends over time.

Tip for best accuracy: Take measurements in the morning before eating or exercising. Use a flexible measuring tape and keep it snug but not tight. Measure each site 2–3 times and use the average.

Frequently Asked Questions

What's the difference between body fat % and BMI?

BMI (Body Mass Index) is calculated solely from your height and weight. It cannot distinguish between fat and muscle. Body fat percentage directly measures how much of your weight is fat, making it a more meaningful indicator of health and fitness.

Why do men and women have different ideal body fat ranges?

Women naturally carry more essential fat due to physiological differences including reproductive hormones. Women require approximately 10–13% essential fat compared to 2–5% for men. This is normal and healthy — not something to reduce.

Why is hip measurement only needed for women?

The U.S. Navy formula for women includes hip circumference because women tend to store more fat in the hip and thigh region (gynoid fat distribution). The male formula uses only waist and neck because men store fat primarily in the abdominal region.

Can I lose fat without losing muscle mass?

Yes — this is called body recomposition. A moderate caloric deficit combined with adequate protein intake (1.6–2.2 g/kg body weight) and resistance training helps preserve lean mass while losing fat. The Body Fat to Lose figure in the results assumes your lean mass stays constant.

How often should I measure my body fat?

Every 4–8 weeks is a reasonable tracking interval. Measuring too frequently can be discouraging due to normal daily fluctuations caused by hydration, food intake, and hormonal cycles. Consistency in measurement conditions (time of day, hydration) is key.

Is low body fat always better?

No. Body fat that is too low — below essential fat levels — can impair immune function, hormone production, and organ health. For most people, the Fitness or low-Average category represents an optimal, sustainable goal.