Body fat calculator
Your body fat percentage, lean mass, FFMI and visceral-fat risk from a tape measure, in five quick questions.
Body fat percentage calculator
Question 1 of 5First, which formula should we use?
Men and women carry fat differently, so the tape-measure method has a version for each.
Your measurements stay on this page.
How tall are you, and what do you weigh?
Grab a tape measure. What's your waist?
Measure level with your belly button, after a normal breath out. Don't pull it in: an inch off your waist moves the answer by about two points.
Your waist ÷ height so far: 0.51
Now your neck.
Neck: just below the Adam's apple, the tape sloping slightly down at the front. Hips: around the widest part of your bottom.
Those measurements don't add up: check that your waist is bigger than your neck.
Last one: what are you working on?
Your results will say what matters for it.
Estimated body fat
20.4% likely 17–24%
Those measurements don't add up: check that your waist is bigger than your neck.
- Lean mass
- 147 lb
- muscle, organs, bone, water
- Fat mass
- 38 lb
- of your weight
- FFMI
- 21.3
- typical for men
- Waist ÷ height
- 0.51
- raised risk of visceral fat
Losing fat
The scale can't tell fat from muscle. A DEXA scan every 8 to 12 weeks shows both, so you know the pounds coming off are the right ones.
Building muscle
FFMI is a rough read on muscle. A DEXA scan measures lean mass arm by arm and leg by leg, so you can see which side is lagging.
On a GLP-1
In the two big GLP-1 trials that scanned people, a quarter to two-fifths of the weight lost was lean mass. Check how much of yours could be →
Where you stand
This estimate can be 3.5 points off either way. A 10-minute DEXA scan measures it, along with the fat around your organs and your bone density.
What a tape measure can't tell you
| Measure | This estimate | DEXA scan |
|---|---|---|
| Body fat | 17–24% | ±1–2 points |
| Fat around your organs | A risk sign | Measured |
| Muscle in each arm and leg | — | Measured |
| Bone density | — | Included |
Updated October 8, 2026 · Sources below · Editorial standards
Body fat percentage chart
The ranges the American Council on Exercise uses. Where you land matters less than which way it moves, which is why people who track body fat measure it the same way every time.
| Category | Men | Women |
|---|---|---|
| Essential | 2–5% | 10–13% |
| Athletes | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Obese | 25%+ | 32%+ |
How this calculator works (U.S. Navy method)
- Body fat uses the U.S. Navy method, developed by the Navy and long used for military fitness standards: your height, neck and waist (and hips, for women), put through a formula fitted to lab measurements.
- Lean mass is everything that isn't fat: muscle, organs, bone and water. It is your weight minus your estimated fat.
- FFMI (fat-free mass index) is lean mass in kilograms divided by height in meters squared, adjusted to 1.8 m so tall and short people compare. It's the "how much muscle for my height" number.
- Waist ÷ height is a quick sign of fat around the organs. Keeping your waist under half your height is the line the UK's NICE guideline uses; 0.6 and above is high risk.
An example: a man who is 5′ 10″ and 185 lb, with a 36 in waist and a 15.5 in neck, comes out at about 20.4% body fat (Average on the chart above, and likely between 17% and 24%), 147 lb of lean mass, an FFMI of 21.3 and a waist-to-height ratio of 0.51.
Why your estimate can be off
A tape measures your outline, not what's inside it. Two people with the same waist can carry very different amounts of muscle and of fat around their organs, so formulas like this one are usually within 3 to 4 percentage points, and further off for very lean, very muscular or older people.
A DEXA body composition scan measures fat, lean mass and bone directly, arm by arm and leg by leg, to within about 1 to 2 points, and puts a number on the fat around your organs. It takes about 10 minutes and needs no referral when you pay cash: see DEXA prices near you.
Losing weight on a GLP-1?
On Ozempic, Wegovy, Mounjaro or Zepbound, the scale can't tell you whether you're losing fat or muscle. See how much of your weight loss may be muscle, based on the trials that measured it.
Body fat calculator: FAQ
How accurate is a body fat calculator?
Tape-measure methods like the U.S. Navy formula usually land within about 3 to 4 percentage points of a lab measurement, and can be further off for very lean or very muscular people. A DEXA scan measures body fat to within about 1 to 2 points.
What is a healthy body fat percentage?
On the American Council on Exercise chart, 14–24% covers the fitness and average ranges for men, and 21–31% for women. Athletes run lower. Essential fat, the minimum the body needs, is 2–5% for men and 10–13% for women.
What is FFMI?
Fat-free mass index is your lean mass in kilograms divided by your height in meters squared, adjusted to a height of 1.8 m. It shows how much muscle you carry for your height. Before that height adjustment, most adults land roughly between 17 and 22 (men) or 14 and 18 (women), which is what “typical” means here; in a 1995 study of athletes, adjusted values above 25 were rare without steroids.
How do I measure my waist and neck?
Use a soft tape, snug but not pressing in. Waist: around your navel after a normal breath out. Neck: just below the Adam's apple, sloping slightly down at the front. Women also measure their hips at the widest point. Measure each twice and use the average.
Sources
- Hodgdon JA, Beckett MB. Prediction of percent body fat for U.S. Navy men and women from body circumferences and height. Naval Health Research Center, 1984. The tape formula.
- American Council on Exercise. Percent body fat norms for men and women. The chart's categories.
- Kouri EM et al. Fat-free mass index in users and nonusers of anabolic-androgenic steroids. Clinical Journal of Sport Medicine, 1995. The normalised FFMI and its ceiling near 25.
- Schutz Y, Kyle UUG, Pichard C. Fat-free mass index and fat mass index percentiles in Caucasians aged 18–98 y. International Journal of Obesity, 2002. The typical FFMI ranges.
- National Institute for Health and Care Excellence (NICE). Overweight and obesity management (opens in a new tab). The waist-to-height thresholds.
Medical Disclaimer: The information provided on this website is for general informational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. DEXA scan results should be interpreted by a qualified healthcare professional.