Body Fat Calculator
Enter your height, weight, age, sex and neck, waist and hip measurements to estimate your body fat percentage two ways, see which ACE category it falls in, and split your weight into fat and lean mass.
Last updated November 4, 2026
Used only by the formula
Result
About 28.2% body fat (U.S. Navy method): Average
| Result | Value |
|---|---|
| Body fat, U.S. Navy method | 28.2% |
| ACE category | Average (women) |
| Fat mass (Navy) | 42.3 lb |
| Lean mass (Navy) | 107.7 lb |
| Body fat, BMI method (Deurenberg) | 29.7% |
| BMI | 23.5 |
| Category | Body fat |
|---|---|
| Essential fat | 10-13% |
| Athletes | 14-20% |
| Fitness | 21-24% |
| Average | 25-31% |
| Obese | 32%+ |
General estimate only, not medical advice. Talk to a qualified health professional about your own situation. Tape and BMI formulas can be several percentage points off a DEXA scan. The BMI method ignores muscle, so it tends to overstate fat in muscular people. ACE categories are shown for the Navy result.
Show the work
Formula: Navy (women): body fat % = 495 / (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.22100 × log10(height)) − 450, all in cm.
- Measurements in cm: height 170.18, neck 35.56, waist 81.28, hip 96.52 (inches × 2.54 if you entered inches).
- Waist + hip − neck = 81.28 + 96.52 − 35.56 = 142.24 cm.
- log10(142.24) = 2.15302 and log10(170.18) = 2.23091.
- Density term = 1.29579 − 0.35004 × 2.15302 + 0.22100 × 2.23091 = 1.03518.
- Body fat = 495 / 1.03518 − 450 = 28.18% (digits shown rounded; the result keeps full precision).
- Fat mass = 68.039 kg × 28.18% = 19.17 kg; lean mass = 68.039 − 19.17 = 48.87 kg.
- BMI = 68.039 / (1.7018)² = 23.49. Deurenberg: 1.20 × 23.49 + 0.23 × 30 − 10.8 × 0 − 5.4 = 29.7% (fat mass 44.5 lb).
- Category: 28.2% is "Average" in the ACE table for women.
Result: About 28.2% body fat (U.S. Navy method): Average
How body fat is estimated
Navy (men) = 495 / (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450
The U.S. Navy method estimates body density from tape measurements, then converts density to a body fat percentage. For men it uses waist minus neck; for women it uses waist plus hip minus neck, with density = 1.29579 − 0.35004 × log10(waist + hip − neck) + 0.22100 × log10(height). All lengths are in centimeters inside the formula, so inches are multiplied by 2.54 first. Body fat percent is 495 divided by density, minus 450.
The second estimate uses only BMI, the Deurenberg formula for adults: body fat % = 1.20 × BMI + 0.23 × age − 10.8 × sex − 5.4, where sex is 1 for men and 0 for women. It needs no tape measure, but it cannot tell muscle from fat, so it overstates fat in muscular people and understates it in people who have lost muscle.
Fat mass is your weight times the body fat percentage, and lean mass is what remains. Lean mass includes muscle, bone, organs and water, not just muscle.
See how we calculate for the formulas, sources and review schedule behind every calculator.
Also useful alongside this calculator: BMI Calculator, Ideal Weight Calculator and Body Surface Area Calculator.
This is an estimate, not medical advice
This calculator gives a general estimate from the published methods listed under Sources. It does not diagnose anything or replace advice from a doctor, dietitian or other qualified health professional, and individual needs differ. This page has not been reviewed by a medical professional.
How to take the measurements
Measure with a flexible tape held level and snug but not tight against the skin, and breathe out normally before reading. Neck goes just below the larynx, sloping slightly down at the front. Waist for men is taken at the navel; for women, at the narrowest point of the torso. Hip is the widest point around the buttocks. Because the formula takes a logarithm of small differences, a one centimeter slip can move the result by about a percentage point, so measure twice and use the average.
Body fat categories
The category shown follows the American Council on Exercise ranges. For men they are essential fat 2 to 5%, athletes 6 to 13%, fitness 14 to 17%, average 18 to 24% and obese 25% and above. For women they are 10 to 13%, 14 to 20%, 21 to 24%, 25 to 31% and 32% and above. The page treats each band as running up to the next band, so 13.5% for a man counts as athletes.
These are descriptive labels for comparison, not diagnoses. Essential fat is the minimum needed for normal body function, and sitting at that level is not a goal for most people.
How accurate is this estimate?
Both formulas are population averages. Tape methods and BMI formulas can differ from a DEXA scan by several percentage points, and the two estimates here will often disagree with each other. Use the Navy figure for tracking over time with identical measuring habits, and treat the BMI figure as a cross-check.
These formulas were built for adults, and this page accepts ages 18 to 100. They do not apply to children, pregnancy, or people with conditions that change fluid balance or body shape.
Sources
Official and primary sources for the statements on this page. Their authors have not reviewed or endorsed this page.
- Deurenberg P, Weststrate JA, Seidell JC. Body mass index as a measure of body fatness: age- and sex-specific prediction formulas. Br J Nutr 1991;65(2):105-114. Title, authors and journal were checked against the DOI record; this is the paper the BMI-based formula 1.20 × BMI + 0.23 × age − 10.8 × sex − 5.4 is attributed to
We could not open the Deurenberg paper itself, so its coefficients are from memory and unverified against the original.
The U.S. Navy circumference method follows Hodgdon and Beckett (Naval Health Research Center reports 84-11 for men and 84-29 for women, 1984). We could not open these reports, so the coefficients are unverified against the originals and are not cited as a source.
The category ranges (essential fat, athletes, fitness, average, obese) follow the American Council on Exercise table; the ACE site could not be opened, so they are unverified and not cited. This page treats the bands as continuous, which is our own reading.
How to use the Body Fat Calculator
- Choose US or metric units, then your sex and age.
- Enter your height and weight.
- Measure your neck and waist, and your hip if you chose female, then enter them.
- Read the Navy estimate, category, fat and lean mass, compare it with the BMI figure, then use Copy, Print or Share.
Worked example
A 30-year-old man, 180 cm, 80 kg, neck 40 cm and waist 90 cm. Waist minus neck is 50 cm, so density = 1.0324 − 0.19077 × 1.69897 + 0.15456 × 2.25527 = 1.05686, and body fat = 495 / 1.05686 − 450 = 18.4%. That is in the average band for men. His BMI is 24.7, so the Deurenberg formula gives 1.20 × 24.69 + 0.23 × 30 − 10.8 − 5.4 = 20.3%.
| Result | Value |
|---|---|
| Body fat, U.S. Navy method | 18.4% |
| ACE category (men) | Average |
| Fat mass at 18.4% | 14.7 kg |
| Lean mass at 18.4% | 65.3 kg |
| BMI | 24.7 |
| Body fat, BMI method | 20.3% |
Frequently asked questions
Which method is more accurate, the Navy method or the BMI method?
Neither is exact. The Navy method uses your actual body shape, so it usually reflects fat distribution better than BMI, but only if your tape measurements are careful.
Why do my two body fat results differ?
The Navy formula looks at neck, waist and hip, while the BMI formula only sees weight, height, age and sex. Muscular or very lean builds often cause the largest gap.
What is a healthy body fat percentage?
It depends on age, sex and fitness, and no single number is right for everyone. Use the categories as a rough guide and ask a health professional what suits you.
Can I use this calculator if I am under 18 or pregnant?
No. The formulas were built for adults and ignore growth and pregnancy changes, so the results would not be reliable for either situation.
Are my numbers stored or sent anywhere?
No. The calculation runs in your browser and nothing you enter is saved or uploaded.