The US Navy method estimates body fat from a few tape measurements. For men it uses height, neck and waist; for women it adds the hips. A man of 175 cm with a 38 cm neck and a 92 cm waist comes out at about 22% body fat, in the average range for men.
Measure yourself, enter the numbers in cm or inches and add your weight if you want your fat mass in kg. The result shows your body fat percentage and its category from the American Council on Exercise.
How to measure
Use a soft tape measure, stand relaxed, and do not pull the tape tight into the skin. Measure twice and use the average.
- Height: without shoes.
- Neck: just below the Adam's apple, with the tape sloping slightly down at the front.
- Waist, men: around the belly at the level of the navel, after breathing out normally.
- Waist, women: at the narrowest point, usually between the ribs and the navel.
- Hip, women: around the widest part of the buttocks.
All measurements must be in the same unit.
The US Navy formula
The equations were published by Hodgdon and Beckett at the Naval Health Research Center in 1984 and are used by the US Department of Defense. With all measurements in inches:
- Men: body fat % = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76
- Women: body fat % = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387
If you enter cm, the calculator converts to inches first (1 inch = 2.54 cm).
Worked example
A physiology teaching lab at Irvine Valley College uses this example: a man 70 inches tall with a 31 inch waist and a 17 inch neck.
| Step | Working | Result |
|---|---|---|
| Waist − neck | 31 − 17 | 14 |
| 86.010 × log10(14) | 86.010 × 1.146 | 98.58 |
| 70.041 × log10(70) | 70.041 × 1.845 | 129.23 |
| Body fat | 98.58 − 129.23 + 36.76 | 6.1% |
A woman 160 cm tall with a 32 cm neck, 78 cm waist and 100 cm hips comes out at about 33.0%. That is just into the obese band for women, which starts at 32%.
Body fat categories for men and women
Categories from the American Council on Exercise. Women need more essential fat than men, so every band is higher.
| Category | Men | Women |
|---|---|---|
| Below essential fat | Below 2% | Below 10% |
| Essential fat | 2% to 5% | 10% to 13% |
| Athletes | 6% to 13% | 14% to 20% |
| Fitness | 14% to 17% | 21% to 24% |
| Average | 18% to 24% | 25% to 31% |
| Obese | 25% and above | 32% and above |
Body fat, BMI and South Asians
BMI only uses weight and height, so it cannot tell fat from muscle. Body fat percentage looks at what the weight is made of. The WHO expert consultation on Asian populations in 2004 found that many Asian groups have a higher body fat percentage at the same BMI than white Europeans, which is why lower BMI cut-offs are advised for Pakistanis. A Pakistani adult with a normal-looking BMI can still carry a high share of fat, so a tape-based estimate is a useful second check alongside the BMI calculator.
How accurate is it?
The Navy method was checked against underwater weighing when it was developed. For one person it can still be several percentage points away from a lab method such as a DEXA scan, and it is least reliable in very lean, very muscular or very heavy people. Small errors with the tape also matter, especially at the neck. Use it to track change over time, measuring the same way each time, rather than as an exact figure.
If you want to lower your body fat, the calorie calculator sets a daily target for a steady rate of loss.
This calculator gives an estimate from a published formula. It does not diagnose any condition and is not a substitute for a doctor. Talk to a doctor before making decisions about your health, diet or treatment.
Body fat questions
How do I calculate my body fat percentage at home?
Measure your height, neck and waist with a tape, and your hips too if you are a woman. Enter them in the calculator, which applies the US Navy formula. Measure in the morning, before eating, relaxed and after breathing out, and repeat each measurement to check it.
What is a healthy body fat percentage?
The American Council on Exercise puts average body fat at 18% to 24% for men and 25% to 31% for women, with fitness levels at 14% to 17% for men and 21% to 24% for women. Obesity starts at 25% for men and 32% for women. Going below essential fat, about 2% for men and 10% for women, is harmful.
Why do women need a hip measurement?
Women tend to store more fat around the hips and thighs, so the waist and neck alone miss much of it. The women's equation adds the hip to the waist and takes away the neck, which fits the data from the original 1984 studies better. The men's equation uses only the waist and neck.
Is the Navy method better than BMI?
It adds information BMI does not have, because it looks at where your size is, not just your weight. It is still an estimate and can be off by several percentage points. Using both, along with your waist size, gives a better picture than either one alone.
Can I use this for a child?
No. The Navy equations were built from adult men and women, and children's bodies change as they grow. For anyone under 18, a doctor uses growth charts for BMI-for-age and, if needed, other measurements to check body fat.
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Last reviewed 30 September 2026. Results are estimates; official notices always take precedence.