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- Body Fat Calculator: US Navy Tape-Measure Method
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Body Fat Calculator: US Navy Tape-Measure Method
This body fat calculator gives you an estimated body fat percentage, fat mass and lean mass from a few tape measurements, using the US Navy method. All you need is a flexible tape measure and two minutes.
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Every number calculated by code from published formulas.
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How it's calculated
The calculator uses the US Navy circumference equations. For men: 495 ÷ (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450. For women, hips are added: 495 ÷ (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.221 × log10(height)) − 450. All measurements are in centimetres. The hip measurement is only used for women. Results are kept between 2% and 60%.
Fat mass is your body weight × body fat percentage, and lean mass is everything else: muscle, bone, organs and water. Your weight does not change the body fat percentage itself; it only splits your weight into these two parts.
Measure carefully, because small errors move the result. Measure your waist horizontally at the navel, relaxed, after breathing out. Measure your neck just below the larynx, with the tape sloping slightly down to the front. For women, measure the hips at the widest point of the buttocks. Take each measurement twice and use the average, ideally in the morning before eating.
The Navy method is a practical field estimate, not a lab measurement. It typically lands within a few percentage points of methods such as DEXA for many people, but can be further off for very muscular people, people with unusual fat distribution, and older adults. Its real strength is tracking: measured the same way every few weeks, the trend tells you far more than any single number.
If you are trying to lose fat while keeping muscle, pair this with the protein calculator and regular strength training, such as the gym workout plan for women. For a quick health-risk check from your waist alone, the waist-to-height ratio in the BMI calculator is a useful companion.
| Range | Men | Women |
|---|---|---|
| Athletic | Below 14% | Below 21% |
| Fit | 14–17.9% | 21–24.9% |
| Average | 18–24.9% | 25–31.9% |
| Above the average range | 25% and above | 32% and above |
Frequently asked questions
How accurate is the Navy body fat calculator?
The Navy method is reasonably accurate for an estimate that only needs a tape measure, often within a few percentage points of lab methods for many people. Accuracy drops for very muscular people and those who carry fat unevenly, and measuring technique matters a lot. It is best used to track change over time, measured the same way each time.
What is a healthy body fat percentage?
There is no single cut-off, but commonly used ranges put roughly 14–24% for men and 21–31% for women as fit to average. Women naturally carry more essential fat than men, and body fat tends to rise with age. Very low body fat is not healthier; it can disrupt hormones, especially in women. Use the ranges as context, not a diagnosis.
Where do I measure my waist for body fat?
For this calculator, measure horizontally around your navel, standing relaxed, at the end of a normal breath out. Keep the tape snug but not pressing into the skin, and do not pull your stomach in. Measure at the same spot and time of day each time, ideally in the morning before eating, so your results are comparable.
Why does the Navy method use neck measurement?
The neck measurement acts as a rough stand-in for lean body mass. A thicker neck tends to go with more muscle, so subtracting it from the waist (and hips, for women) helps separate fat from frame size. It is a simple shortcut, which is also why the method can misjudge people with very muscular necks or unusual builds.
What is the most accurate way to measure body fat?
DEXA scans, hydrostatic weighing and air displacement (Bod Pod) are among the most accurate methods available, though each still has some error. Skinfold callipers can be good in experienced hands. Bioimpedance scales and tape methods are less precise but cheap and convenient. Whatever you choose, stick with one method, because switching between methods makes trends hard to read.
How quickly can I lower my body fat percentage?
A sustainable pace is about 0.25–0.5 kg of weight loss a week; how much that moves your percentage depends on your size and starting point, and lighter people see bigger percentage shifts per kilo. Faster loss usually costs muscle. Keep protein high, keep strength training, and remeasure every two to four weeks rather than daily, because tape error hides small changes.
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General fitness information, not medical advice. Check with a doctor if you have a medical condition, are pregnant or have an injury.