Body Fat Calculator
Estimate your body fat percentage with a tape measure using the US Navy method, cross-checked with two other formulas. See your category, the healthy range for your age, and a goal weight.
- Instant results
- 3 methods compared
- Goal weight
- Nothing stored
Calculated on your device. Measurements are never stored or uploaded.
Enter your measurements
Your body fat percentage, category and goal weight appear here as soon as the required fields are filled in.
How to use the body fat calculator
- Measure with a tapeMeasure your neck and waist (and hips for women) with a soft tape, keeping it level and snug without pressing into the skin.
- Enter your measurementsChoose your sex – the formulas differ for men and women – then add height, the tape measurements, and optionally weight and age.
- Read and compareSee your body fat percentage, category and healthy range, compare three methods, and set a goal to see the matching weight.
How to measure for an accurate result
Use a soft, non-stretch tape measure. Stand upright and relaxed, breathe out normally and keep the tape level and snug without squeezing the skin. Take each measurement twice and use the average.
Just below the larynx (Adam’s apple), with the tape angled slightly downward at the front.
Horizontally around the belly at the level of the belly button.
At the narrowest part of the waist, usually a little above the belly button.
Around the widest part of the buttocks, with feet together.
Body fat categories and healthy ranges
The American Council on Exercise (ACE) groups body fat into five broad categories:
| Category | Women | Men |
|---|---|---|
| Essential fat | 10–13% | 2–5% |
| Athletes | 14–20% | 6–13% |
| Fitness | 21–24% | 14–17% |
| Average | 25–31% | 18–24% |
| Obese | 32% and above | 25% and above |
Healthy ranges also shift with age. These widely used ranges come from Gallagher and colleagues (American Journal of Clinical Nutrition, 2000):
| Age | Women – healthy | Men – healthy |
|---|---|---|
| 20–39 | 21–33% | 8–20% |
| 40–59 | 23–34% | 11–22% |
| 60–79 | 24–36% | 13–25% |
The formulas
US Navy, men: 495 ÷ (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450
US Navy, women: 495 ÷ (1.29579 − 0.35004 × log₁₀(waist + hips − neck) + 0.22100 × log₁₀(height)) − 450
Relative Fat Mass: men 64 − 20 × height ÷ waist; women 76 − 20 × height ÷ waist
BMI-based (Deurenberg): 1.2 × BMI + 0.23 × age − 10.8 × sex − 5.4 (sex = 1 for men, 0 for women)
All lengths in centimetres.
Getting the most from it
- Measure at the same time of day – ideally in the morning before eating – so changes reflect real progress.
- Watch the trend over several weeks rather than a single reading.
- Very muscular people and people with an unusual fat distribution may get less accurate estimates.
This calculator gives general estimates and is not medical advice. Speak to a doctor or registered dietitian about your health.
Frequently asked questions
How accurate is the US Navy body fat method?
It is an estimate. In studies it usually lands within about 3–4 percentage points of lab methods such as DEXA scans, and it is most reliable when you measure carefully and the same way each time. It is best for tracking changes over weeks and months.
Where exactly should I measure?
Neck: just below the larynx (Adam’s apple), with the tape sloping slightly down to the front. Waist: men at the level of the belly button; women at the narrowest point of the waist. Hips (women): at the widest part of the buttocks. Stand relaxed and don’t suck in your stomach.
What is a healthy body fat percentage?
It depends on age and sex. For adults aged 20–39, healthy ranges are roughly 8–20% for men and 21–33% for women, and they rise a little with age. Enter your age to see the range for your age group.
Why do the three methods give different numbers?
Each formula was built from different measurements and populations. The Navy method uses neck, waist and hips; Relative Fat Mass uses only height and waist; the BMI-based method uses weight, height and age. They usually agree within a few points – a bigger gap often means one tape measurement is off.
Why do I need to choose male or female?
Men and women store fat differently, so the published formulas use different equations and different healthy ranges. Choose the sex the formulas should use.
How is the goal weight worked out?
The calculator keeps your current lean mass (everything that isn’t fat) the same and works out the total weight at your chosen body fat percentage. In reality you may gain or lose a little muscle too, so treat it as a guide.
Can I use it for children or during pregnancy?
No. These formulas were developed for adults and don’t apply to children, teenagers or pregnant women.
Are my measurements saved?
No. Everything is calculated in your browser and nothing is stored or sent anywhere.
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