Body Fat Percentage Calculator
US Navy tape method, with ACE categories.
The calculator never sends or saves what you type.
Tracking weight lost instead? Weight loss as a percentage. Your waist against your height? Waist to height ratio.
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How the US Navy method works
Male: %BF = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76, inchesFemale: %BF = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387, inches
The US Navy fitted these equations on tape measurements of its own personnel, so all the method needs is a tape and your height. Every measurement is in inches; a centimetre value is divided by 2.54 first. For a man 180 cm tall with a 38 cm neck and an 86 cm waist:
- In inches (÷ 2.54): height 70.8661, neck 14.9606, waist 33.8583
- Waist − neck: 33.8583 − 14.9606 ≈ 18.8976 in
- log10(18.8976) ≈ 1.2764; log10(70.8661) ≈ 1.8504
- 86.010 × 1.2764 − 70.041 × 1.8504 + 36.76 ≈ 16.9372%
- Rounded to 1 decimal place.
- The published standard error, for the men’s equation, is about 3.5 points: read any figure as an estimate within a few points.
So about 16.9%, in ACE’s Fitness range for men (14% to under 18%).
To turn the percentage into kilograms, multiply your weight by it: at 80 kg, 16.9% is about 13.5 kg of fat and 66.5 kg of everything else (lean mass). Both are estimates, as uncertain as the percentage.
The method also has a metric form, fitted through body density rather than directly on body fat, and the two forms do not agree to one decimal. For a woman 165 cm tall with a 33 cm neck, a 74 cm waist and 96 cm hips, the inch form gives 27.2% and the density form 26.9%. Calculators that switch formula when you switch units print two numbers for one body. This one converts centimetres to inches and uses the inch form for both, so 70, 15 and 34 inches and 177.8, 38.1 and 86.36 centimetres both give 17.5%. Try it: the woman’s measurements.
These are the equations of Hodgdon and Beckett (1984), the ones the Navy’s own assessment tables were built from through 2025. Those tables were read after rounding height up and the circumference down to the half inch, in whole percents, so an official figure from them could differ slightly from this one. Since January 2026 the Navy’s official assessment (NAVADMIN 264/25) works differently: it has two steps, first a waist-to-height ratio that is the same for men and women, then a body-composition calculation from Navy-developed equations that differ by sex. The measurements collected are height, weight and waist. This calculator still computes the classic 1984 tape formula and does not reproduce that test; for an official Navy result, use the Navy’s own assessment.
Source: Hodgdon JA, Beckett MB. Prediction of percent body fat for U.S. Navy men from body circumferences and height (Report 84-11), and for U.S. Navy women (Report 84-29). Naval Health Research Center, San Diego, 1984.
How to measure body fat at home with a tape measure
- Height: Your height without shoes. In inches you can type feet and inches, like 5′10.
- Neck: Around the neck just below the larynx (Adam’s apple), the tape level all the way round.
- Waist: Men: around the abdomen at the navel. Women: at the narrowest point of the waist. Relaxed, after breathing out.
- Hip: Women only: around the widest part of the hips and buttocks. Not used for men.
Use a flexible tape, snug on the skin without pressing in. Measuring each site two or three times and using the average makes the estimate steadier, and measuring at the same time of day makes one week comparable with the next.
Other ways to measure body fat include skinfold calipers, bioimpedance scales and DEXA scans. They do not always agree with a tape or with each other, so compare a reading only with one taken the same way. The UK’s NICE guideline on overweight and obesity (NG246) advises: “Do not use bioimpedance as a substitute for BMI as a measure of general adiposity in adults.”
Body fat percentage chart for men and women
The American Council on Exercise (ACE) groups adult body fat into five categories, separately for women and men. The calculator names your category with every answer.
| Category | Women | Men |
|---|---|---|
| Essential fat | 10% to under 14% | 2% to under 6% |
| Athletes | 14% to under 21% | 6% to under 14% |
| Fitness | 21% to under 25% | 14% to under 18% |
| Average | 25% to under 32% | 18% to under 25% |
| Obese | 32% and above | 25% and above |
Source: American Council on Exercise (ACE), general body-fat percentage categories (acefitness.org).
ACE prints these as whole-number ranges (18–24% for an average man); the table and the calculator read each one up to the next category’s start, so 24.5% for a man is still Average. And the calculator never rounds a figure onto the start of a category: an estimate of 25.0109% for a man is shown as 25.01%, not 25.0%, because 25% is exactly where Obese begins.
These are general categories for adults, not a target set for you and not a diagnosis.
Body fat percentage by age
ACE’s categories are the same at every adult age, but body fat tends to rise with age at the same weight: in the BMI method’s formula below, each year adds 0.23 points, so from 25 to 55 the same BMI estimates 6.9 points more. The figures most “body fat by age” charts reprint come from a study by Gallagher and colleagues (2000), who measured body fat in the laboratory in 1,626 adults and published the body fat that goes with each BMI cut-off at each age: 18.5 (below it is underweight), 25 (overweight) and 30 (obesity).
African American and white adults (Table 4)
| Age | At BMI 18.5 | At BMI 25 | At BMI 30 |
|---|---|---|---|
| Female | |||
| 20–39 | 21% | 33% | 39% |
| 40–59 | 23% | 34% | 40% |
| 60–79 | 24% | 36% | 42% |
| Male | |||
| 20–39 | 8% | 20% | 25% |
| 40–59 | 11% | 22% | 28% |
| 60–79 | 13% | 25% | 30% |
Asian adults (Table 5)
| Age | At BMI 18.5 | At BMI 25 | At BMI 30 |
|---|---|---|---|
| Female | |||
| 20–39 | 25% | 35% | 40% |
| 40–59 | 25% | 35% | 41% |
| 60–79 | 25% | 36% | 41% |
| Male | |||
| 20–39 | 13% | 23% | 28% |
| 40–59 | 13% | 24% | 29% |
| 60–79 | 14% | 24% | 29% |
Read across a row: for a woman aged 20–39, the body fat that matches a healthy BMI (18.5 to under 25) is 21% to under 33%; for a man of that age, 8% to under 20%. Under 60, the Asian participants carried more body fat at the same BMI than the white and African American participants (25% to under 35% and 13% to under 23% at 20–39); at 60–79 the two tables are within a point of each other. The Asian sample was Japanese, so treat that table as a direction, not a rule for India or the rest of Asia.
These are predictions from BMI, age and sex, not a target set for you. The authors call them “provisional healthy percentage body fat ranges”, and say the ranges at low BMI “have large CIs and should be applied cautiously”.
Charts of an “ideal” percentage for each age credited to Jackson and Pollock also circulate; we could not trace them to a table in the original studies, so none is reproduced here.
Source: Gallagher D, Heymsfield SB, Heo M, Jebb SA, Murgatroyd PR, Sakamoto Y. Healthy percentage body fat ranges: an approach for developing guidelines based on body mass index. American Journal of Clinical Nutrition 2000;72(3):694–701, Tables 4 and 5. doi:10.1093/ajcn/72.3.694
Body fat from height and weight: the BMI method
%BF = 1.20 × BMI + 0.23 × age − 10.8 × sex − 5.4
With no tape, body fat can be estimated from BMI (weight in kg ÷ height in m²), age and sex, with sex 1 for men and 0 for women. This is Deurenberg’s formula for adults, 16 and over. Its standard error is about 4.1 points against 3.5 for the tape method, and it cannot tell muscle from fat, so a muscular person reads high. Estimates at three ages:
Male
| BMI | Age 25 | Age 40 | Age 55 |
|---|---|---|---|
| 20 | 13.6% | 17.0% | 20.5% |
| 22.5 | 16.6% | 20.0% | 23.5% |
| 25 | 19.6% | 23.0% | 26.5% |
| 27.5 | 22.6% | 26.0% | 29.5% |
| 30 | 25.6% | 29.0% | 32.5% |
| 35 | 31.6% | 35.0% | 38.5% |
Female
| BMI | Age 25 | Age 40 | Age 55 |
|---|---|---|---|
| 20 | 24.4% | 27.8% | 31.3% |
| 22.5 | 27.4% | 30.8% | 34.3% |
| 25 | 30.4% | 33.8% | 37.3% |
| 27.5 | 33.4% | 36.8% | 40.3% |
| 30 | 36.4% | 39.8% | 43.3% |
| 35 | 42.4% | 45.8% | 49.3% |
The formula is for adults, 16 and over; its authors give a different one for children aged 15 and under, which this page does not compute.
Source: Deurenberg P, Weststrate JA, Seidell JC. Body mass index as a measure of body fatness: age- and sex-specific prediction formulas. British Journal of Nutrition 1991;65(2):105–114.
How accurate is a tape-measure estimate?
Against laboratory measurements, the Navy’s men’s equation has a published standard error of about 3.5 points, so the man’s 16.9% above is best read as roughly 13–20% (we found no published figure for the women’s equation). That is why the calculator calls every figure an estimate, prints it in plain ink rather than the green it uses for checked arithmetic, and shows no check mark: there is no exact answer to check it against. Its strength is consistency. The same tape, the same sites and the same time of day give a trend you can trust more than any single reading.
When you compare two readings, keep percentage points and percent apart: a fall from 25% to 21% is 4 percentage points, which is a 16% decrease in the reading itself. Percentage points vs percent change.
We checked the inch form against every cell of the Navy’s 2016 assessment tables (Guide 4, Tables 2 and 3): rounded to whole percents, it reproduces 916 of 916 for men and 1,080 of 1,080 for women. The equations were fitted on 602 Navy men aged 18 to 56 and 214 Navy women aged 18 to 44, so outside those ages the estimate is an extrapolation.
This is an estimate for tracking, not a medical assessment. If a reading worries you, or you are pregnant, under 18 or very muscular, where these equations were not fitted or are least reliable, a clinician can measure body composition directly. Disclaimer
Frequently asked questions
How do I calculate body fat percentage?
Measure your height, neck and waist (women also the hip), then use the US Navy formula in inches. For men it is 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76. A man 180 cm tall with a 38 cm neck and an 86 cm waist comes out at about 16.9%. The calculator above converts the units, does the logarithms and shows each step.
How accurate is the Navy body fat calculator?
It is an estimate. Against laboratory measurements the men’s equation has a published standard error of about 3.5 points, so a man’s reading of 16.9% is best read as roughly 13–20%; we found no published figure for the women’s equation. The arithmetic itself is the Navy’s: rounded to whole percents, this calculator reproduces all 916 cells of the Navy’s 2016 table for men and all 1,080 for women. It is most useful for tracking one person, measured the same way, over time.
What is a healthy body fat percentage for women?
The usual reference is the American Council on Exercise’s categories. For women, 21% to under 25% is “fitness” and 25% to under 32% “average”; 10% to under 14% is essential fat, and 32% and above is ACE’s obese category. They are general categories, not a target set for you.
What is a healthy body fat percentage for men?
On the American Council on Exercise’s categories, 14% to under 18% is “fitness” and 18% to under 25% “average” for men; 2% to under 6% is essential fat, and 25% and above is ACE’s obese category. They are general categories, not a target set for you.
What is the ideal body fat percentage by age?
There is no single ideal, and ACE’s categories are the same at every adult age. The widely reprinted by-age figures come from Gallagher and colleagues (2000), who published the body fat that matches a healthy BMI (18.5 to under 25) at each age: 21% to under 33% for women aged 20–39, rising to 24% to under 36% at 60–79, and 8% to under 20% for men aged 20–39, rising to 13% to under 25%. The authors call these ranges provisional: they are predictions from BMI, not a target set for you.
Can I work out body fat from height and weight?
Roughly, with the BMI method (Deurenberg, 1991): 1.20 × BMI + 0.23 × age − 10.8 × sex − 5.4, with sex 1 for men and 0 for women. At a BMI of 22.5 and age 40 it gives 20.0% for a man and 30.8% for a woman. Its standard error is about 4.1 points against 3.5 for the tape method, and it cannot tell muscle from fat.
Where do I measure my neck for body fat?
Just below the larynx (Adam’s apple), with the tape level all the way round rather than sloping down at the front. Keep it snug on the skin without pressing in, and measure at the same place every time.
Where do I measure my waist for body fat?
Men measure around the abdomen at the navel; women at the natural waist, the narrowest point. Stand relaxed, measure after breathing out, and keep the tape level and snug without pressing in. Women also measure the hip, around the widest part of the hips and buttocks.
Why do other calculators give a different answer in cm and inches?
The Navy method exists in two forms: one fitted in inches and one in centimetres through body density, and they do not agree to one decimal. For a woman 165 cm tall with a 33 cm neck, a 74 cm waist and 96 cm hips, the inch form gives 27.2% and the density form 26.9%. A calculator that switches formula with the unit gives one body two answers; this one converts to inches and uses one formula whatever you type in.
Does the Navy still use the neck and waist tape test?
Its official assessment has changed. Since January 2026 (NAVADMIN 264/25) the Navy’s body composition assessment has two steps: first a waist-to-height ratio, the same for men and women, then a body-composition calculation from Navy-developed equations that differ by sex. The measurements collected are height, weight and waist. This calculator computes the classic 1984 tape formula (Hodgdon and Beckett), the one the Navy’s tables were built from through 2025, so it does not give an official Navy result. The Army uses its own method under its regulation AR 600-9, which this calculator does not compute either.