HEALTH · FREE ONLINE CALCULATOR

Body Fat Percentage Calculator

Calculate your body fat percentage with the U.S. Navy method using height, neck, waist and (for women) hip measurements. See fat mass, lean mass and how your result compares with general body fat categories for men and women.

Detailed optionsStep-by-step guideWorked examples

01 / BODY FAT PERCENTAGE

Calculate your body fat percentage

You need a soft tape measure. Measure in the morning, relaxed, without pulling the tape tight.

UnitsHeight (cm)Neck (cm)Waist (cm)Weight (kg, optional)Age (optional)

Estimated body fat16.4%

U.S. Navy circumference method

Fitness

Fat mass: 13.1 kg · lean mass: 66.9 kgBMI-based estimate for comparison: 21% (BMI 25.2)Typical error of tape methods: about ±3–4 percentage points.

02 / WHERE DO YOU FALL?

Body fat categories for men

General reference ranges published by the American Council on Exercise (ACE). Healthy ranges also change with age.

ACE body fat categories
Category	Body fat
Essential fat	2–5%
Athletes	6–13%
Fitness	14–17%
Average	18–24%
Obese	25% +

YOUR ANIMATED GUIDE

How the Navy body fat formula works.

These steps use your current inputs. Choose a step or play the walkthrough.

STEP 1 / 4

47 cm

1234

Measure the circumferences

Men: waist horizontally at the navel and the neck just below the larynx.

Waist 85 − neck 38 = 47 cm

Explore at your own pace

How to use this body fat calculator

A body fat percentage calculator estimates how much of your body weight is fat, using only a tape measure. This page uses the U.S. Navy circumference method: neck and waist measurements for men, plus hips for women, together with your height. Add your weight to see fat mass and lean mass, and compare your result with general body fat categories for men and women.

How to calculate body fat percentage at home

Use a flexible tape measure on bare skin. Measure your neck just below the larynx (Adam’s apple), sloping slightly down to the front. Men measure the waist horizontally at the navel; women measure the waist at its narrowest point and the hips at the widest point of the buttocks. Keep the tape snug but not compressing the skin, take each measurement two or three times and use the average.

How the U.S. Navy method works

The Navy method was developed from measurements of service members and estimates body density from circumferences and height. Body density is then converted to body fat percentage with the Siri equation. It is quick, cheap and repeatable, which makes it useful for tracking change over time. Like all circumference methods, it can be off by several percentage points for an individual, especially for very muscular people.

Body fat percentage vs BMI

BMI uses only height and weight, so it cannot tell muscle from fat. Body fat percentage looks at body composition directly. Two people with the same BMI can have very different body fat. If you also enter weight and age, the calculator shows a BMI-based body fat estimate for comparison.

Body Fat formulas, explained

Men (metric, cm)

Body fat % = 495 ÷ (1.0324 − 0.19077 log₁₀(waist − neck) + 0.15456 log₁₀(height)) − 450

Women (metric, cm)

Body fat % = 495 ÷ (1.29579 − 0.35004 log₁₀(waist + hip − neck) + 0.22100 log₁₀(height)) − 450

Fat and lean mass

Fat mass = weight × body fat % · lean mass = weight − fat mass

BMI-based estimate (adults)

1.20 × BMI + 0.23 × age − 10.8 × sex − 5.4

sex = 1 for men, 0 for women (Deurenberg equation).

EVERY OPTION, EXPLAINED

Know what goes into your result.

Use this reference to check units, assumptions and advanced settings.

Body Fat calculator input reference
Input or option	What it means
Sex	Selects the male or female version of the Navy equation. The female equation adds a hip measurement.
Units	Metric (centimeters and kilograms) or imperial (inches and pounds). Switching converts the values you entered.
Height	Standing height without shoes. For imperial, use total inches: 5 ft 10 in = 70 in.
Neck	Circumference just below the larynx.
Waist	Men: at the navel. Women: at the narrowest point.
Hips	Women only: at the widest part of the buttocks.
Weight	Optional. Used to split your weight into fat mass and lean mass.
Age	Optional. Used only for the BMI-based comparison estimate (adults 18–100).

PUT THE FORMULA TO WORK

Worked examples you can try.

Load an example into the calculator, then change one value to explore.

EXAMPLE 01

Man, 178 cm

Neck 38 cm, waist 85 cm, 80 kg: about 16.4% body fat (fitness range), roughly 13.1 kg of fat mass.

EXAMPLE 02

Woman, 165 cm

Neck 33 cm, waist 75 cm, hips 100 cm, 62 kg: about 29.4% body fat (average range).

MAKE THE NUMBERS MAKE SENSE

Common mistakes to avoid

Measuring the waist at the wrong place: at the navel for men, at the narrowest point for women.
Pulling the tape tight or measuring over clothing.
Comparing results taken at different times of day. Measure at the same time, ideally in the morning.

A LITTLE MORE CLARITY

Frequently asked questions

Who is this body fat calculator for?

Adults who want a quick, repeatable estimate from tape measurements. It is not designed for children or pregnancy, and it is not a medical assessment.

Do I need my weight?

No. Weight is optional. Add it to split your body weight into fat mass and lean mass.

How do I calculate my body fat percentage?

Measure your height, neck and waist (and hips if you are a woman) with a tape measure, then enter them above. The calculator applies the U.S. Navy formula and shows your estimated body fat percentage and category.

How accurate is the Navy body fat calculator?

For most adults it is typically within about 3 to 4 percentage points of laboratory methods such as DEXA, but individual errors can be larger. It is best used to track changes using consistent measurements.

What is a healthy body fat percentage?

General ACE ranges: for men, 14–17% is “fitness” and 18–24% “average”; for women, 21–24% is “fitness” and 25–31% “average”. Healthy ranges rise somewhat with age; discuss personal targets with a health professional.

Can I calculate body fat without calipers?

Yes. The Navy method uses only a tape measure. Skinfold calipers, bioimpedance scales and DEXA scans are alternatives with their own strengths and limitations.

Where do I measure my waist and neck for body fat?

Neck: just below the larynx, tape sloping slightly downward to the front. Waist: men at the navel; women at the narrowest part of the torso. Hips (women): the widest part of the buttocks.

Is body fat percentage better than BMI?

It gives more information, because it separates fat from lean mass. BMI is still useful as a quick screening tool. Using both, with waist size, gives a fuller picture.

How often should I measure body fat?

Every 2 to 4 weeks is enough to see a trend. Day-to-day changes are mostly measurement noise and water.

Methodology & assumptions

Calculations run in your browser using the formulas and assumptions explained on this page. Intermediate values retain full floating-point precision; displayed amounts are rounded. Body fat is estimated with the U.S. Navy circumference equations (Hodgdon & Beckett) in their metric form, converted from body density with the Siri equation. Imperial inputs are converted with 1 in = 2.54 cm and 1 lb = 0.45359237 kg. Categories are the general American Council on Exercise ranges. This is an adult educational estimate, not a medical assessment, and it is not designed for children, pregnancy or some athletes. Sharing an input link places those inputs in the URL.