BMI (Body Mass Index) is a simple estimate of body size based on weight and height. It does not directly measure body fat.

What is a healthy BMI range?

For many adults, a BMI from 18.5 to 24.9 is considered a healthy range. Individual health can vary.

Why do athletes sometimes have a high BMI?

BMI does not distinguish muscle from fat. People with more muscle may have a higher BMI even when healthy.

Home›Body Fat Calculator

Body Fat Calculator

Estimate body fat percentage using tape measurements (U.S. Navy method). Optionally compare with a BMI-based estimate when age is provided.

Privacy: All calculations run locally in your browser. We do not send your inputs to any server.

Tip: your entries are never placed in the page URL.

Height (cm)

Enter your height in centimeters.

Weight (kg) (optional)

Optional—used to estimate fat mass and lean mass.

Sex

Used to pick the correct formula and reference ranges.

Age (optional)

Enables the BMI-based estimate and an age-based “ideal” reference.

Neck (cm)

Measure below the larynx with the tape slightly sloping down to the front.

Waist (cm)

Men: measure at the navel. Women: measure at the narrowest point.

Hip (cm) (female only)

Measure at the widest point around the hips.

Export summary downloads a .txt file created in your browser. Copy page link copies only the page address (no inputs).

About body fat

Body fat percentage is the portion of your body weight that is fat tissue. It’s different from BMI: two people can have the same BMI but very different body compositions.

How the U.S. Navy method works

You measure height plus a few circumferences with a tape measure (neck and waist; for women, hips as well).
These measurements are plugged into a formula that uses log10(). This gives an estimate of body fat percentage.
Results are approximate. Small measurement errors (or different measuring points) can move the result.

Imperial (inches)
  Male:   BFP = 86.010·log10(waist − neck) − 70.041·log10(height) + 36.76
  Female: BFP = 163.205·log10(waist + hip − neck) − 97.684·log10(height) − 78.387

Metric (cm)
  Male:   BFP = 495 / (1.0324 − 0.19077·log10(waist − neck) + 0.15456·log10(height)) − 450
  Female: BFP = 495 / (1.29579 − 0.35004·log10(waist + hip − neck) + 0.22100·log10(height)) − 450

BMI method (optional)

If you enter age and weight, the calculator also shows a second estimate based on BMI. This is a rough estimate and is mainly useful for comparison.

Adults
  Male:   BFP = 1.20·BMI + 0.23·Age − 16.2
  Female: BFP = 1.20·BMI + 0.23·Age − 5.4
Children
  Boy:    BFP = 1.51·BMI − 0.70·Age − 2.2
  Girl:   BFP = 1.51·BMI − 0.70·Age + 1.4

Category ranges

The category shown in this tool uses the American Council on Exercise (ACE) body fat categorization:

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

Ideal body fat (age-based reference)

If age is provided, the “ideal” reference is based on a Jackson & Pollock table (values increase with age). This is not a medical target—just a commonly used reference.

Age	Women	Men
20	17.7%	8.5%
25	18.4%	10.5%
30	19.3%	12.7%
35	21.5%	13.7%
40	22.2%	15.3%
45	22.9%	16.4%
50	25.2%	18.9%
55	26.3%	20.9%

Note: “Body fat to lose” assumes your current weight stays constant (a simple estimate).

Body fat (U.S. Navy method)	—
Body fat category (ACE)	—
Body fat mass	—
Lean body mass	—
Ideal body fat for age (Jackson & Pollock)	—
Body fat to lose to reach ideal	—
Body fat (BMI method)	—