Body Fat Calculator
Estimate your body fat percentage in seconds.
How to measure
- Neck: just below the voice box, tape sloping slightly down at the front. Do not flare your neck.
- Waist, men: level with the belly button, relaxed, without pulling your stomach in.
- Waist, women: at the narrowest point of the waist.
- Hip, women: around the widest part of the hips.
- Keep the tape snug and level, and measure on bare skin.
This calculator processes your entries in this page; it does not intentionally send them to a server.
Your Body Fat
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Your estimate, category, and healthy range for your age will appear here.
Estimates only: tape and BMI methods can differ from each other and from clinical assessments. DXA can provide a more detailed body-composition assessment, but it also has limitations. FFMI is a height-adjusted estimate of fat-free mass; it is not a diagnosis or a stand-alone health score.
Medically reviewed by Dr. Muhammad Sharif (FCPS, MCPS). Last reviewed: 17-Oct-2026
Quick answer: A body fat calculator estimates the share of your weight that is fat in the body composition. Enter your age, sex, height, weight, and neck and waist measurements (plus hips for women). For adults aged 20 to 39, a healthy range is about 8 to 19.9% for men and 21 to 32.9% for women. The result is an estimate, not a diagnosis.
How to Use This Body Fat Calculator
- Choose US units or metric units.
- Pick male or female.
- Choose Tape Measure (Navy) for the best estimate, or BMI based estimates if you have no tape.
- Enter your age, weight, and height, then your neck and waist (and hip for women).
- Press Calculate Body Fat.
Your numbers stay in your browser, and we do not save them. The tool is for adults aged 18 and older.
What You Will See in Your Results
- Your body fat percentage and category: essential, athletes, fitness, average, or higher.
- The healthy range for your age and sex.
- Fat mass and lean mass.
- BMI and FFMI, a height adjusted measure of lean mass.
- A BMI based cross check when you use the tape method.
- A goal weight, only if your estimate is above the healthy range for your age.
How to Measure Body Fat at Home
You need a soft tape measure. Measure on bare skin, keep the tape snug and level, and do not pull your stomach in.
- Neck: just below the voice box, with the tape sloping slightly down at the front. Do not flare your neck.
- Waist for men: level with the belly button.
- Waist for women: at the narrowest part of the waist.
- Hips for women: around the widest part of the hips.
Measure in the morning before you eat or exercise. Take each measurement twice and use the average. Use the same spots every time you track changes.
What Is a Healthy Body Fat Percentage?
After you use the body fat calculator, compare your result with the two tables below. They answer different questions.
Fitness categories. The American Council on Exercise groups body fat by how lean a person is.
| Category | Women | Men |
|---|---|---|
| Essential fat | 10 to 13% | 2 to 5% |
| Athletes | 14 to 20% | 6 to 13% |
| Fitness | 21 to 24% | 14 to 17% |
| Average | 25 to 31% | 18 to 24% |
| Higher | 32% and up | 25% and up |
ACE calls the last row obese. This page and the tool say higher.
Health based ranges by age. These come from a 2000 study by Gallagher and colleagues. They link healthy body fat to a healthy BMI of 18.5 to 24.9, and the authors call them provisional.
| Age | Women | Men |
|---|---|---|
| 20 to 39 | 21 to 32.9% | 8 to 19.9% |
| 40 to 59 | 23 to 33.9% | 11 to 21.9% |
| 60 to 79 | 24 to 35.9% | 13 to 24.9% |
Body fat tends to rise with age, so the ranges rise too. Very low body fat can also affect health, so a lower number is not always better.
Example Results
Here are two sample results from the tool.
| Man | Woman | |
|---|---|---|
| Age | 30 | 35 |
| Height | 5′-10″ | 5′-5″ |
| Weight | 170 lb | 140 lb |
| Neck | 15 in | 13 in |
| Waist | 34 in | 30 in |
| Hip | Not needed | 38 in |
| Navy estimate | 17.5% | 28.6% |
| Category | Fitness | Average |
| Fat mass | 29.8 lb | 40 lb |
| Lean mass | 140.3 lb | 100 lb |
| BMI based estimate | 20.0% | 30.6% |
The BMI based estimate runs higher in both cases. The tool shows both numbers so you can see the gap, and it flags a gap of more than 5 points.
How Is Body Fat Percentage Calculated?
U.S. Navy method
Hodgdon and Beckett developed this tape method at the Naval Health Research Center in 1984, and a Department of Defense report describes it. With inches, the equations are:
- Men: body fat % = 86.010 × log10(waist minus neck) minus 70.041 × log10(height) plus 36.76
- Women: body fat % = 163.205 × log10(waist plus hip minus neck) minus 97.684 × log10(height) minus 78.387
With centimeters, the tool uses the metric versions:
- Men: body fat % = 495 ÷ (1.0324 minus 0.19077 × log10(waist minus neck) plus 0.15456 × log10(height)) minus 450
- Women: body fat % = 495 ÷ (1.29579 minus 0.35004 × log10(waist plus hip minus neck) plus 0.22100 × log10(height)) minus 450
BMI based method
The Deurenberg equation estimates body fat from BMI, age, and sex:
Body fat % = 1.20 × BMI plus 0.23 × age minus 10.8 × sex minus 5.4
Sex is 1 for men and 0 for women. Its typical error in the original study was 4.1 percentage points, and it slightly overestimated body fat in people with obesity. Read more about BMI and how it is calculated.
Fat mass and lean mass
- Fat mass = weight × body fat % ÷ 100
- Lean mass = weight minus fat mass
- FFMI = lean mass in kilograms ÷ height in meters squared
The tool also shows a height adjusted FFMI, which adds 6.1 × (1.8 minus your height in meters).
How Accurate Is a Body Fat Calculator?
A body fat calculator gives an estimate, not a measurement. A 2008 study tested military circumference equations against laboratory methods and found total errors of about 3.5 to 5 percentage points. So a result of 20% could be a few points higher or lower in real life.
Other methods include skinfold calipers, scales that send a small bioelectrical impedance scales through the body, and DEXA(also called DXA) scans. A DEXA scan is more precise but needs a clinic visit.
To get the most from any estimate, use the same method each time and watch the trend over weeks, not days.
Body Fat vs BMI
BMI compares your weight with your height. It cannot tell muscle from fat or show where fat sits. Body fat percentage tries to answer how much of your weight is fat, but it is also an estimate. Doctors often look at both, plus waist size. Try our BMI calculator, see the BMI chart, or find a target with the Ideal Weight Calculator.
Who Should Not Use a Body Fat Calculator
- People under 18. The equations were built for adults.
- Pregnant women. Weight and body shape change for normal reasons.
- Very muscular people. The BMI based estimates option can overestimate body fat. Use the tape method instead.
- Anyone preoccupied with weight or body fat. If thoughts about numbers take over your day, talk with a doctor.
Waist measurements can also shift with bloating or recent weight change. Military services use their own tape tests and rules, so this tool is not an official assessment. Follow your service’s current regulation.
Frequently Asked Questions
What is a good body fat percentage for women?
For women aged 20 to 39, a health based range is 21 to 32.9%. ACE labels 21 to 24% as fitness and 25 to 31% as average. The range rises to 23 to 33.9% at ages 40 to 59 and 24 to 35.9% at ages 60 to 79.
What is a good body fat percentage for men?
For men aged 20 to 39, a health based range is 8 to 19.9%. ACE labels 14 to 17% as fitness and 18 to 24% as average. The range rises to 11 to 21.9% at ages 40 to 59 and 13 to 24.9% at ages 60 to 79.
How accurate is the Navy body fat calculator?
It is an estimate. Studies of military circumference equations found total errors of about 3.5 to 5 percentage points against laboratory methods. Careful, repeated measurements help, but a DEXA scan is more precise.
Is body fat percentage better than BMI?
They answer different questions. BMI compares weight with height and cannot tell muscle from fat. Body fat percentage estimates how much of your weight is fat, but it is still an estimate. Doctors often use both.
How can I calculate body fat without a tape measure?
Use the BMI based estimates option. It uses your height, weight, age, and sex. It is less precise, and it can overestimate body fat in muscular people.
Does this body fat calculator save my numbers?
No. The math runs in your browser, and nothing you enter is saved on our servers.
How often should I measure my body fat?
Every few weeks is enough. Use the same method, the same body spots, and the same time of day, and look at the trend instead of one reading.
Final Thoughts
A body fat calculator is a quick way to see how your weight splits between fat and lean mass. Use the tape method for the best estimate, compare your result with the ranges for your age, and watch the trend over time. Then pair it with your BMI, waist size, and advice from your doctor.
This page is for information only and is not medical advice. Talk with a doctor about your results. Read our Medical Disclaimer and Medical Review Policy.
Sources
- American Council on Exercise. Percent body fat calculator and categories.
- 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 to 701.
- Hodgdon J, Friedl K. Development of the DoD Body Composition Estimation Equations. Technical Report 99-2B. 1999.
- 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 to 114.
- Percent body fat estimations in college men using field and laboratory methods: A three-compartment model approach. Dynamic Medicine. 2008;7:7. Link: https://dynamic-med.biomedcentral.com/articles/10.1186/1476-5918-7-7
- Kouri EM, Pope HG, Katz DL, Oliva P. Fat-free mass index in users and nonusers of anabolic-androgenic steroids. Clinical Journal of Sport Medicine. 1995;5(4):223 to 228.
- Centers for Disease Control and Prevention. About BMI.