Body fat calculator

Your body fat percentage from a few tape measurements, and how much of your weight is fat.

Your body fat

27.3%

about 39 lb of your 143 lb

Fat 39 lb
Lean mass 104 lb

With a 13 in neck, a 28.5 in waist and 38.5 in hips at 5 ft 5 in, the U.S. Navy formula puts your body fat at about 27.3%.

That’s about 39 lb of fat and 104 lb of everything else: muscle, bone, organs and water. Tape methods can be off by a few points either way.

I’m not a doctor or a dietitian. This is an estimate, for information only. For decisions about your health, check with a professional.

Your numbers

example: change the numbers

Units

The math stays the same. Only the way the numbers are shown changes.

Metrickg · cmUSlb · ftUKst · ft

Sex

Men and women have different formulas and measuring points.

FemaleMale

Height

Neck

Just below the Adam’s apple, with the tape level.

Waist

Men: around the belly at the navel. Women: around the narrowest part of the waist. Stand relaxed.

Hips (women only)

Around the widest part of the buttocks. Not used for men.

Weight

To split your weight into fat and lean mass.

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Your measurements and the result
	Height	5 ft 5 in
	Neck	13 in
	Waist, at the narrowest point	28.5 in
	Hips, at the widest point	38.5 in
	Body fat	27.3%
	Fat	39 lb
	Lean massmuscle, bone, organs and water	104 lb

How it works

Measure your neck just below the Adam’s apple and your waist: at the navel for men, at the narrowest point for women. Women also measure their hips at the widest part of the buttocks. Keep the tape level and snug, without squeezing.
Men: body fat % = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76. Women: body fat % = 163.205 × log10(waist + hips − neck) − 97.684 × log10(height) − 78.387. Everything is in inches; centimeters are converted exactly (1 in = 2.54 cm).
With your weight, the percentage splits it into fat and lean mass, which is everything else: muscle, bone, organs and water.

Worked example

A woman, 5 ft 5 in (65 in), neck 13 in, waist 28.5 in, hips 38.5 in: 163.205 × log10(28.5 + 38.5 − 13) − 97.684 × log10(65) − 78.387 = 163.205 × log10(54) − 97.684 × log10(65) − 78.387 = 282.74 − 177.09 − 78.39 = 27.3%. At 143 lb, that’s about 39 lb of fat and 104 lb of lean mass. A man who is 5 ft 10 in, with a 15 in neck and a 34 in waist: 86.010 × log10(19) − 70.041 × log10(70) + 36.76 = 17.5%.

Sources

Text checked on September 30, 2026

Good to know

Tape methods are off by a few points. Compared with DXA scans in 609 fit US Marines, this formula read on average about 2.5 points low for men and 1.3 to 2.3 points high for women, with individual results spread about 4 to 5 points either way.
The same study found it overestimates lean people and underestimates people with more body fat.
Measure the same way every time: even between experienced measurers, results differ by about 1 point. The trend over a few weeks tells you more than one reading.
This page doesn’t label your number good or bad: published body fat ranges differ from one source to another.

Frequently asked questions

How accurate is the Navy body fat method?

Within a few points for most people, not better. In a 2022 study of fit US Marines checked against DXA scans, it read about 2.5 points low for men and up to about 2 points high for women on average. The authors call it a quick way to screen people, not a precise measurement.

How do I measure my neck, waist and hips?

Stand relaxed, with the tape level and snug but not squeezing. Neck: just below the Adam’s apple. Waist: at the navel for men, at the narrowest point for women. Hips, for women: at the widest part of the buttocks. Measure each one a couple of times and use the average.

What is a healthy body fat percentage?

There isn’t one official range: published charts differ by source, age and sex, so this page doesn’t label your result. For health screening, the WHO and the NHLBI look at BMI together with waist size. Your doctor can put your number in context.

Why is it different from my smart scale?

Scales and handheld devices use bioelectrical impedance, a different method with its own errors. In the same Marine study, a research-grade impedance device came closer to DXA than the tape method did.

Does my waist size matter on its own?

The NHLBI says a waist over 35 inches for women or 40 inches for men increases health risk. The NHLBI measures the waist just above the hip bones, a different spot from the Navy method, so take a separate measurement for that check.