In this article
Your weight doesn’t tell you what it’s made of. Two people of the same height and weight can look completely different — one muscular, one carrying more fat. Body fat percentage gives a better picture, and you can estimate it at home with nothing more than a flexible measuring tape.
This article is general information, not medical advice. Talk to a doctor or qualified fitness professional about your health and goals.
The US Navy method
Developed to assess personnel quickly without lab equipment, the US Navy method estimates body fat from height and a few circumference measurements:
- Men: neck and waist
- Women: neck, waist and hips
The formulas use logarithms of these measurements, so you’ll want a calculator — but the measuring is the part that matters.
How to measure correctly
You’ll need a flexible tailor’s tape. Measure on bare skin, standing relaxed, and don’t pull the tape tight.
| Measurement | Where |
|---|---|
| Height | Without shoes, standing straight against a wall |
| Neck | Just below the Adam’s apple (larynx), tape sloping slightly downward at the front |
| Waist (men) | Horizontally at the level of the navel |
| Waist (women) | At the narrowest point of the waist |
| Hips (women) | Around the widest part of the buttocks |
Breathe out normally before measuring the waist — don't suck in your stomach. Take each measurement twice and use the average.
Worked examples
Man: 175 cm, 78 kg, neck 38 cm, waist 88 cm → about 19.2% body fat — roughly 15 kg of fat and 63 kg of lean mass.
Woman: 163 cm, 60 kg, neck 32 cm, waist 72 cm, hips 96 cm → about 26.9% body fat — roughly 16 kg of fat and 44 kg of lean mass.
What the numbers mean
The American Council on Exercise uses these broad categories:
| Category | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athletes | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Obese | 25%+ | 32%+ |
Women naturally carry more essential fat than men — very low body fat isn’t healthy for anyone.
Why body fat beats weight alone
If you start strength training and eat well, you may gain muscle while losing fat. Your weight might hardly change, but your waist shrinks and your body fat percentage drops. Tracking only weight would make you think nothing was happening.
Limitations
- Very muscular people (with thick necks) can get underestimates.
- Unusual fat distribution can reduce accuracy.
- Measurement errors of a centimetre or two noticeably change the result — which is why consistency matters.
For precise results, lab methods like DEXA scans are more accurate. For tracking progress at home, the tape method works well.
Calculate yours
Our Body Fat & Ideal Weight Calculator uses the US Navy formula to estimate your body fat percentage, fat mass and lean mass, and also shows your ideal weight range using four common formulas and the healthy BMI range.
Free toolTry the Body Fat & Ideal WeightEstimate body fat from a few tape measurements and see your ideal weight range.Frequently asked questions
How accurate is the tape method?
For most people it's usually within a few percentage points of lab methods. It's less accurate for very muscular people or those with unusual body shapes.
Should I trust a smart scale instead?
Smart scales use bioelectrical impedance, which changes with hydration, meals and exercise. Readings can swing by several percent day to day. Use the trend, not single readings.
How often should I measure?
Every two to four weeks, at the same time of day, is enough to see real changes.
For general information only — not medical advice, diagnosis or treatment. Always consult a qualified doctor, pharmacist or healthcare professional. Written by the Toolsopedia team. Spotted an error? Tell us and we’ll fix it.