UNDERSTAND THE METHOD
How to use this calculator
Select the method that matches your equipment and measurements. Tape sites and skinfold sites are different inputs. For the 3-site method, men use chest, abdomen, and thigh; women use triceps, thigh, and suprailiac. The 4-site method uses triceps, suprailiac, abdomen, and thigh. The 7-site method uses all seven named sites. Durnin–Womersley uses biceps, triceps, subscapular, and suprailiac.
What the result can tell you
Each method estimates body composition with population and measurement error. The Bailey formula is a historical comparison whose accuracy claim is not independently verified here. The equations are not interchangeable and do not diagnose health. A constant-lean-mass comparison does not predict how actual weight change divides between fat and lean tissue.
Body fat methods compared, and ranges by age
Every method here except Bailey is an equation fitted to lab measurements in one group of people. None measures your fat directly, and none is the most accurate for everyone. Choose by the equipment you have, then keep using the same method.
What each method needs and what it was built on
| Method | You need | Built on |
|---|---|---|
| U.S. Navy · tape | Height. Tape at neck and navel (men) or neck, waist and hips (women) | Department of Defense circumference equations for military body-composition checks |
| CUN-BAE · height and weight | Height, weight, age and sex | 6,510 white adults aged 18 to 80, measured by air-displacement plethysmography (2012) |
| Jackson–Pollock · 3 or 7 sites | Skinfold calipers | Lab body density in 308 men aged 18 to 61 (1978) and, by underwater weighing, 249 women aged 18 to 55 (1980) |
| Jackson–Pollock · 4 sites | Skinfold calipers | A Jackson–Pollock equation that gives percent fat directly from four skinfolds and age; this page does not cite its source sample |
| Durnin–Womersley · 4 sites | Skinfold calipers | Body density in 481 men and women aged 16 to 72, with a separate equation for each age band (1974) |
| Covert Bailey · tape | Tape at more sites, including the wrist | A historical formula; its accuracy claim is not independently verified |
Here is one hypothetical man run through six methods in this calculator: age 40, 178 cm, 82 kg, neck 39 cm and waist at the navel 92 cm. His skinfolds in mm: chest 14, abdomen 24, thigh 16, triceps 12, suprailiac 18, subscapular 16, midaxillary 14, biceps 6.
Same man, six methods
| Method | Body fat | Fat mass |
|---|---|---|
| U.S. Navy · tape | 21.0% | 17.2 kg (38.0 lb) |
| CUN-BAE · height and weight | 24.7% | 20.3 kg (44.7 lb) |
| Jackson–Pollock · 3 sites | 17.4% | 14.3 kg (31.5 lb) |
| Jackson–Pollock · 4 sites | 18.6% | 15.3 kg (33.6 lb) |
| Jackson–Pollock · 7 sites | 17.9% | 14.7 kg (32.4 lb) |
| Durnin–Womersley · 4 sites | 25.1% | 20.6 kg (45.4 lb) |
His estimates run from 17.4% to 25.1%, a gap of 7.7 percentage points from one set of measurements. Equations can disagree this much for one person, so compare a new result only with an earlier one from the same method.
The ranges below are the provisional ones Gallagher and colleagues (2000) published for African American and white adults. The calculator uses the same ranges in its first result table. The researchers predicted body fat from BMI, age and sex, and set each cut point where BMI reaches 18.5, 25 and 30. Underfat matches a BMI below 18.5, overfat a BMI of 25 to below 30, and obese a BMI of 30 or more. Each age band uses the prediction for age 30, 50 or 70.
Men: body fat ranges by age
| Age | Underfat | Healthy | Overfat | Obese |
|---|---|---|---|---|
| 20–39 | Below 8% | 8% to below 20% | 20% to below 25% | 25% and above |
| 40–59 | Below 11% | 11% to below 22% | 22% to below 28% | 28% and above |
| 60–79 | Below 13% | 13% to below 25% | 25% to below 30% | 30% and above |
Women: body fat ranges by age
| Age | Underfat | Healthy | Overfat | Obese |
|---|---|---|---|---|
| 20–39 | Below 21% | 21% to below 33% | 33% to below 39% | 39% and above |
| 40–59 | Below 23% | 23% to below 34% | 34% to below 40% | 40% and above |
| 60–79 | Below 24% | 24% to below 36% | 36% to below 42% | 42% and above |
What does 20% body fat mean? For a man it falls in ACE's average category, which does not change with age. In Gallagher's ranges for African American and white adults it is overfat at age 20 to 39, where 20% is the cut point itself, and healthy at 40 to 59 and 60 to 79. For a woman, 20% is in ACE's athletes band and underfat at every age in Gallagher's ranges, where healthy starts at 21% even at age 20 to 39. The tables below read other percentages the same way. Each percentage is a share of body weight: at 80 kg, 20% is 16 kg of fat and 64 kg of fat-free mass.
Men: what each body fat percentage means (ACE, then Gallagher by age)
| Body fat | ACE | Age 20–39 | Age 40–59 | Age 60–79 |
|---|---|---|---|---|
| 10% | Athletes | Healthy | Underfat | Underfat |
| 15% | Fitness | Healthy | Healthy | Healthy |
| 20% | Average | Overfat | Healthy | Healthy |
| 25% | Obese | Obese | Overfat | Overfat |
| 30% | Obese | Obese | Obese | Obese |
| 35% | Obese | Obese | Obese | Obese |
| 40% | Obese | Obese | Obese | Obese |
Women: what each body fat percentage means (ACE, then Gallagher by age)
| Body fat | ACE | Age 20–39 | Age 40–59 | Age 60–79 |
|---|---|---|---|---|
| 10% | Essential | Underfat | Underfat | Underfat |
| 15% | Athletes | Underfat | Underfat | Underfat |
| 20% | Athletes | Underfat | Underfat | Underfat |
| 25% | Average | Healthy | Healthy | Healthy |
| 30% | Average | Healthy | Healthy | Healthy |
| 35% | Obese | Overfat | Overfat | Healthy |
| 40% | Obese | Obese | Obese | Overfat |
Use these as reference points, not a diagnosis. The paper's ranges for Asian adults are mostly higher, especially at younger ages, and the authors noted that one universal set of ranges is hard to build. They also warned that the lowest cut points are the least certain. A tape or caliper estimate has its own error, so a result close to a cut point could belong on either side of it.
Common questions
How do I choose a body-fat method?
Select the method that matches your equipment and measurements. The 3-site method uses different sites by sex category; the 4-site, 7-site, and Durnin–Womersley methods use their own named sites.
Which body fat method is most accurate?
None is most accurate for everyone. In their source studies, CUN-BAE had a standard error of 4.66 percentage points, and the Jackson, Pollock and Ward women's equations that also use hip circumference about 3.6 to 4.0 points. The same-man example on this page gives one man estimates from 17.4% to 25.1%. Use the method that fits your equipment and compare results within that method.
How do I calculate lean body mass from height and weight?
Use a published formula. For men, Boer is 0.407 × weight in kg + 0.267 × height in cm − 19.2; for women, 0.252 × weight + 0.473 × height − 48.3. James and Hume use other coefficients, and Janmahasatian uses weight and BMI. The lean body mass calculator on this page shows all four side by side. They estimate an average adult of your height and weight, so they cannot tell muscle from fat. With a measured body fat percentage, fat-free mass is weight × (1 − body fat ÷ 100).
Can I compare percentages from different methods?
Compare them with care. The equations are not interchangeable, and each estimate has population and measurement error.
Is 20% body fat good?
It depends on sex and age. For a man, 20% is in ACE's average category; in the Gallagher ranges it sits on the cut point between healthy and overfat at 20 to 39 (counted as overfat) and is healthy from 40 to 79. For a woman, 20% is in ACE's athletes band and below the Gallagher healthy range at every age, which starts at 21% for ages 20 to 39. Gallagher's lowest cut points are the least certain, and the ranges are for African American and white adults. The tables above read 10% to 40% for men and women by age.
What is a healthy body fat percentage?
For African American and white adults aged 20 to 39, the Gallagher ranges this calculator uses put healthy at 8% to below 20% for men and 21% to below 33% for women. The ranges rise with age, and the paper's ranges for Asian adults of that age are higher. The tables above list each age group from 20 to 79.
Sources & limitations15 sources
Sources checked September 12, 2026. These notes identify methods and assumptions. They have not received an independent clinical review.
- Gallagher proposed body-fat ranges linked to BMI reference limits.pubmed.ncbi.nlm.nih.gov
- ACE body-fat fitness categories.acefitness.org
- ACSM fitness assessment manual; adapted age-specific categories.acsm.org
- CUN-BAE body-fat equation.doi.org
- Department of Defense circumference equations.apps.dtic.mil
- Jackson–Pollock generalized skinfold equations for men.pubmed.ncbi.nlm.nih.gov
- Jackson–Pollock–Ward generalized skinfold equations for women and their standard errors.pubmed.ncbi.nlm.nih.gov
- Generalized skinfold body-composition equations.pubmed.ncbi.nlm.nih.gov
- Durnin–Womersley body-density equations.pubmed.ncbi.nlm.nih.gov
- Durnin–Womersley and Jackson–Pollock–Ward skinfold equations compared with air-displacement plethysmography in 43 women.pmc.ncbi.nlm.nih.gov
- Boer (1984) estimated lean body mass from body weight and height to normalize body fluid volumes.pubmed.ncbi.nlm.nih.gov
- Hume (1966) predicted lean body mass from height and weight, using total body water measured by antipyrine space in 29 men and 27 women.pmc.ncbi.nlm.nih.gov
- Tahari and colleagues (2014) give the James formula (1976) and note that its lean body mass peaks and then falls at a BMI of about 43 for men and 37 for women.pmc.ncbi.nlm.nih.gov
- Janmahasatian and colleagues (2005) built a fat-free mass formula from sex, height and weight against DXA in 373 adults with BMIs from 17 to 70.pubmed.ncbi.nlm.nih.gov
- Puri and Blake (2022) compared ten lean body mass equations with DXA in 1,558 UK adults aged 60 to 65; Janmahasatian was one of the two that agreed best.pmc.ncbi.nlm.nih.gov