Find your body fat percentage in seconds
This body fat calculator gives you an estimate of how much of your body weight is fat versus lean tissue — things like muscle, bone, and water. Enter a handful of body measurements and you get an instant percentage, a fat-mass figure in kilograms, and a category that tells you where you stand.
Everything runs in your browser. No data leaves your device, and nothing is stored or uploaded anywhere.
How to use this body fat calculator
- Choose your sex — the formula differs for men and women.
- Enter your height in centimetres (cm).
- Measure your neck at its narrowest point, just below the Adam's apple, and enter the value in cm.
- Measure your waist at the navel for men; at the narrowest point for women.
- Women only — measure your hips at the widest part.
- Hit Calculate. You'll see your body fat %, your estimated fat mass and lean mass, and your category.
Tip on measuring: use a soft tape measure, stand relaxed (don't suck in), and take each measurement twice, then average the two. Small errors in measurement can shift the result by 1–2 percentage points.
Body fat percentage categories — at a glance
This table follows commonly cited reference ranges from exercise science literature. Use it to read your result in context.
| Category | Men (% body fat) | Women (% body fat) |
|---|---|---|
| Essential fat (minimum needed for basic health) | 2 – 5 % | 10 – 13 % |
| Athletes | 6 – 13 % | 14 – 20 % |
| Fitness | 14 – 17 % | 21 – 24 % |
| Average | 18 – 24 % | 25 – 31 % |
| Obese | 25 % and above | 32 % and above |
This calculator uses the U.S. Navy circumference method, which estimates body fat from neck, waist, and hip (women only) measurements. Results are estimates — not a clinical measurement.
Worked example
Here's a realistic example so you can see the calculator in action before you enter your own numbers.
Person: Woman, 168 cm tall.
- Neck: 33 cm
- Waist: 74 cm
- Hips: 98 cm
Result: approximately 26 % body fat — placing her in the average category. At a body weight of 65 kg, that works out to roughly 17 kg of fat mass and 48 kg of lean mass.
For a man at 180 cm, neck 38 cm, waist 84 cm, the same formula returns roughly 18 % body fat — low end of the average range.
How it is calculated — the U.S. Navy method
The U.S. Navy developed this formula in the 1980s so personnel could estimate body fat quickly with just a tape measure. It uses circumference measurements instead of expensive equipment like DEXA scans or hydrostatic weighing.
For men:
Body Fat % = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76For women:
Body Fat % = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387All measurements are in centimetres. log10 means the base-10 logarithm — a standard maths function. The formula is published in the U.S. Department of Defense body-composition guidelines and is widely used in fitness research.
Once you have the percentage, fat mass and lean mass follow from your body weight:
Fat mass (kg) = body weight × (body fat % ÷ 100)
Lean mass (kg) = body weight − fat massHow to read your result — and what it can't tell you
Your body fat percentage is a more informative number than weight alone. Two people can weigh exactly the same and have very different body compositions — one mostly muscle, one mostly fat.
That said, every circumference-based method carries some error. Studies typically report the U.S. Navy formula's margin of error at ±3–4 percentage points compared to gold-standard methods like DEXA. Treat the number as a useful direction, not a precise clinical measurement.
The formula also doesn't distinguish where fat is stored. Visceral fat (the fat around internal organs) carries more health risk than fat under the skin, and this calculator can't separate the two. If you have concerns about your body composition or weight, a doctor or registered dietitian can arrange more accurate testing and give you personal guidance.
For broader context on healthy weight ranges, the WHO overweight and obesity fact sheet and the CDC healthy weight pages are reliable starting points.
Practical habits that genuinely help — no fads
If your result is higher than you'd like, a few evidence-backed habits move the needle over time. None of them require drastic action.
- Eat mostly whole foods. Vegetables, legumes, lean protein, and whole grains keep you full longer and make it easier to eat less without feeling deprived.
- Prioritise protein. Adequate protein (roughly 1.2–1.6 g per kg of body weight per day for active adults) helps preserve lean muscle when you're in a calorie deficit.
- Add resistance training. Lifting weights or doing bodyweight exercises builds lean mass, which raises your resting metabolic rate over time.
- Walk more. Daily walking is one of the most consistent habits linked to healthy body composition in large population studies — and it's easy to build into any lifestyle.
- Sleep 7–9 hours. Poor sleep elevates hunger hormones and makes calorie control harder.
- Be patient. Sustainable fat loss is roughly 0.5–1 % of body weight per week. Faster approaches tend to strip muscle alongside fat.
These are general suggestions, not medical advice. A registered dietitian can build a plan matched to your specific goals and health history.
This tool is for educational purposes only. It does not constitute medical advice. If you have any concerns about your health or body composition, please speak with a qualified healthcare professional.
Ready to check your numbers? Use the body fat calculator at the top of this page — your result is instant, private, and free.