Body Fat Percentage Calculator

✦ Health & Wellness

This body fat percentage calculator estimates your body fat from a tape measure with the US Navy equations, then places it on a healthy body fat percentage chart for your age and sex, with fat mass and lean mass.

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The formula

US Navy circumference equations, in the form the Department of Defense adopted (Hodgdon & Friedl 1999)

Men:    %fat = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76
Women:  %fat = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387
        all lengths in inches (cm ÷ 2.54); log10 = base-10 logarithm
Fat mass = weight × %fat ÷ 100      Lean mass = weight − fat mass

These are Hodgdon and Beckett's 1984 Navy equations rewritten to give %fat directly in inches; the Department of Defense adopted them in 1999. Standard error: 3.52 percentage points for men, 3.61 for women, against underwater weighing. Men measure the waist at the navel, women at its narrowest point. The healthy ranges come from Gallagher et al. 2000, Table 3.

Calculating it by hand

Choose male or female (it picks the equation) and metric or US units.
Enter age, height and weight; weight only splits the result into fat mass and lean mass.
Measure the neck just below the larynx and the waist — at the navel for men, at the narrowest point for women — and, for women, the hips at the widest point.
Convert centimetres to inches (÷ 2.54) and take base-10 logarithms of (waist − neck) for men or (waist + hip − neck) for women, and of height.
Apply the equation: 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.
Read the result against the Gallagher range for your age group and sex, and multiply by weight for fat mass.

Worked examples

Man, 30: 178 cm, 75 kg, neck 38 cm, waist 82 cm (metric)

Enter: Male, Metric, age 30, height 178, weight 75, neck 38, waist 82.
Inches: height 178 ÷ 2.54 = 70.08; neck 14.96; waist 32.28; waist − neck = 17.32
%fat = 86.010 × log10(17.32) − 70.041 × log10(70.08) + 36.76 = 106.53 − 129.27 + 36.76 = 14.0%
Fat mass = 75 × 14.03% = 10.5 kg; lean mass = 75 − 10.5 = 64.5 kg
Gallagher, white men 20–39: healthy 8–20.9% → Healthy. ACE: 14–17% → Fitness

14.0% body fat — Healthy (8–20.9% for men 20–39); 10.5 kg fat, 64.5 kg lean mass

Woman, 28: 165 cm, 60 kg, neck 32 cm, waist 70 cm, hip 96 cm (metric)

Enter: Female, Metric, age 28, height 165, weight 60, neck 32, waist 70, hip 96.
Inches: height 64.96; neck 12.60; waist 27.56; hip 37.80; waist + hip − neck = 52.76
%fat = 163.205 × log10(52.76) − 97.684 × log10(64.96) − 78.387 = 281.08 − 177.07 − 78.39 = 25.6%
Fat mass = 60 × 25.63% = 15.4 kg; lean mass = 60 − 15.4 = 44.6 kg
Gallagher, white women 20–39: healthy 21–32.9% → Healthy. ACE: 25–31% → Average

25.6% body fat — Healthy (21–32.9% for women 20–39); 15.4 kg fat, 44.6 kg lean mass

Man, 52: 5 ft 10 in (70 in), 185 lb, neck 16 in, waist 36 in (US units)

Enter: Male, US units, age 52, height 70, weight 185, neck 16, waist 36.
Waist − neck = 36 − 16 = 20 in
%fat = 86.010 × log10(20) − 70.041 × log10(70) + 36.76 = 111.90 − 129.23 + 36.76 = 19.4%
Fat mass = 185 × 19.43% = 35.9 lb; lean mass = 185 − 35.9 = 149.1 lb
Gallagher, white men 40–59: healthy 11–22.9% → Healthy. ACE: 18–24% → Average

19.4% body fat — Healthy (11–22.9% for men 40–59); 35.9 lb fat, 149.1 lb lean mass

Methodology

How the tape-measure estimate works

The Navy equations estimate body fat from where it sits, not from weight — which is why weight does not enter them. Their error, about 3.5 percentage points either way, is larger than the gap between most of the bands it is read against.

Read sources and limits

What is a healthy body fat percentage?

A body fat percentage calculator estimates what share of your weight is fat, here from neck, waist, hip and height measurements using the US Navy equations, and compares it with ranges for your age and sex. Healthy ranges are higher for women than for men and rise with age.

The ranges this page uses are from Gallagher and colleagues (American Journal of Clinical Nutrition, 2000), who measured 1,626 adults and mapped the healthy BMI band onto body fat measured with a four-compartment model. For white adults, Table 3 gives a healthy range of 8% to under 21% for men aged 20–39, 11% to under 23% at 40–59 and 13% to under 25% at 60–79; for women, 21% to under 33%, 23% to under 35% and 25% to under 38%. Obesity begins at 26%, 29% and 31% for men and 39%, 41% and 43% for women.

The same table has separate columns for African American and Asian adults, because body fat at the same BMI differs between groups: an Asian man aged 20–39 is in the healthy range from 13% to under 23%. Choose the column under Advanced. The authors called these ranges provisional.

How does the US Navy body fat calculator work?

It applies the US Navy circumference equations, which James Hodgdon and Marcie Beckett of the Naval Health Research Center fitted in 1984 on 602 Navy men aged 18 to 56 and 214 Navy women aged 18 to 44, against body fat measured by underwater weighing.

In 1999 Hodgdon and Friedl rewrote them to give percent fat directly with lengths in inches, and those are the equations the Department of Defense adopted and this page applies; centimetres are divided by 2.54 first.

For the default man — 178 cm, neck 38 cm, waist 82 cm — that is 70.08 in, 14.96 in and 32.28 in; waist minus neck is 17.32 in. Then 86.010 × log10(17.32) = 106.53 and 70.041 × log10(70.08) = 129.27, so 106.53 − 129.27 + 36.76 = 14.0%. At 75 kg that is 10.5 kg of fat and 64.5 kg of lean mass.

The published standard error is 3.52 percentage points for men and 3.61 for women: about two readers in three measure within that distance of the estimate. Cross-validation samples gave 2.70 points for Navy men and 4.0 to 4.4 for women.

What is a healthy body fat percentage on the ACE chart?

Many fitness tables use the American Council on Exercise (ACE) categories, a professional body's table rather than a study: for men, essential fat 2–5%, athletes 6–13%, fitness 14–17%, average 18–24% and obese 25% or more; for women, 10–13%, 14–20%, 21–24%, 25–31% and 32% or more. They do not change with age.

The chart under the calculator draws both: the Gallagher ranges for your age group, sex and reference group on the first track and the ACE categories on the second, with your estimate marked across both. The default man's 14.0% is healthy on the first and "fitness" on the second.

Is body fat percentage better than BMI?

BMI uses only height and weight, so it cannot see whether weight is fat or muscle; a body fat estimate from circumferences can. For comparison the calculator also shows a BMI-based figure, the Deurenberg formula (British Journal of Nutrition, 1991): 1.20 × BMI + 0.23 × age − 10.8 × sex − 5.4.

Sex is 1 for men and 0 for women, and the formula's standard error is 4.1 percentage points. For the default man, BMI 23.7 at age 30 gives 19.1% by Deurenberg against 14.0% from the tape. A gap of five points is common, and it is the reason the BMI line is labelled an estimate from BMI, not a measurement.

How should you measure, and who does the estimate fit?

Use a flexible tape, snug but not compressing the skin. Neck: just below the larynx, sloping slightly down at the front. Waist: men at the navel, women at the narrowest point between the ribs and the navel, after a normal breath out. Hips (women): around the widest part of the buttocks.

Measure twice and average; a 1 cm change at the waist moves the default man's estimate by 0.84 percentage points.

This calculator gives an estimate from the measurements you enter, using the published equation named beside the result. It is not a diagnosis, a medical assessment or health advice, and it was fitted on young and middle-aged Navy personnel, so it is less reliable for very lean or very heavy people, older adults, children and during pregnancy. A clinician or a direct measurement (DEXA, underwater weighing) gives your actual figure.

Body Fat Percentage questions

What is a healthy body fat percentage for my age?

For white adults in Gallagher et al. (2000), the healthy range is 8–20.9% for men aged 20–39, 11–22.9% at 40–59 and 13–24.9% at 60–79; for women it is 21–32.9%, 23–34.9% and 25–37.9%. The same study gives slightly different ranges for African American and Asian adults, which you can choose under Advanced.

What is the ideal body fat percentage for a man?

There is no single ideal: for a man aged 20–39 the Gallagher healthy range runs from 8% to just under 21%, and the American Council on Exercise calls 14–17% "fitness" and 18–24% "average". Below about 5% is essential fat only. The range moves up with age, to 13–24.9% at 60–79.

What is a healthy body fat percentage for a woman?

21–32.9% for a woman aged 20–39, rising to 23–34.9% at 40–59 and 25–37.9% at 60–79, in Gallagher's table for white adults. The ACE table puts 21–24% as "fitness" and 25–31% as "average", with 10–13% as essential fat. Women carry more essential fat than men, so in Gallagher's table their ranges sit 12 to 13 points higher.

How accurate is the Navy body fat calculator?

About ±3.5 percentage points for two readers in three: the published standard errors are 3.52 points for men and 3.61 for women against underwater weighing. In cross-validation it was 2.70 points for 100 Navy men and 4.0 to 4.4 points for women. Careful, repeated tape measurements matter as much as the equation.

How do you measure body fat with a tape measure?

Three or four measurements: neck just below the larynx; waist at the navel for men or at the narrowest point for women; and, for women, hips at the widest point of the buttocks — plus height. Keep the tape level and snug, measure after a normal breath out, and average two readings. Enter them in centimetres or inches.

How do I calculate body fat percentage by hand?

For a man, take log10(waist − neck) and log10(height) in inches: 86.010 × log10(20) − 70.041 × log10(70) + 36.76 = 111.90 − 129.23 + 36.76 = 19.4% for a 36 in waist, 16 in neck and 70 in height. For a woman, use waist + hip − neck with 163.205, 97.684 and −78.387.

How much fat mass do I have?

Multiply your weight by your body fat percentage: 75 kg at 14.0% is 10.5 kg of fat, leaving 64.5 kg of lean mass — muscle, bone, organs and water. The calculator shows both in kilograms or pounds, and the chart shows where the percentage sits for your age and sex.

Why is my BMI-based estimate different from the tape result?

Because it uses only height, weight, age and sex. The Deurenberg (1991) formula, 1.20 × BMI + 0.23 × age − 10.8 × sex − 5.4, has a standard error of 4.1 points and cannot tell muscle from fat: for the default man it gives 19.1% against 14.0% from the tape. It is shown for comparison, not as a measurement.

What is essential body fat?

2–5% of body weight for men and 10–13% for women in the ACE table: the fat in nerves, bone marrow, organs and, for women, sex-specific tissue that the body needs to function. A tape-measure estimate near those levels is at the edge of what the Navy equations were fitted on, so treat it with extra caution.

Can teenagers use this body fat calculator?

No: the Navy equations were fitted on adults aged 18 to 56 (men) and 18 to 44 (women), and the Gallagher ranges cover ages 20 to 79, so the calculator accepts ages 18 to 100 and uses the 20–39 range at 18 and 19. Children and teenagers grow into their body composition, which needs paediatric references.

Source notes

Method, sources & limitations

Every figure on this page comes from the formula above applied to the values you enter. Nothing is estimated from market data, and no result is a forecast. These are the sources behind the method and any fixed figures it uses:

Written and maintained by CalculatorManager Editorial, Editorial team. Figures last verified 2026-10-20.

Educational information only. Results are estimates produced from the assumptions you enter, and are not financial, tax, legal or medical advice. Check anything that matters against a qualified professional and the cited sources.