Body Fat Calculator

Estimate your body fat percentage using the US Navy tape-measure method, with fat mass and lean mass breakdown.

Your Measurements

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Your Results

Body Fat Percentage
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Category
Fitness
0 kg
Fat Mass
0 kg
Lean Mass
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How the US Navy Body Fat Method Works

This calculator uses the US Navy circumference method, a tape-measure-based formula developed for military fitness testing. It estimates body fat percentage from your height and a few circumference measurements.

Men: %BF = 495 / (1.0324 − 0.19077×log₁₀(waist−neck) + 0.15456×log₁₀(height)) − 450

Women: %BF = 495 / (1.29579 − 0.35004×log₁₀(waist+hip−neck) + 0.22100×log₁₀(height)) − 450

Why does the women's formula add hip measurement?

Women naturally store a larger share of body fat around the hips, while men tend to store more around the abdomen. The women's formula adds hip circumference to capture this difference, while the men's formula relies on waist and neck alone — matching each gender's typical fat distribution pattern.

Where to measure

All measurements should be taken in centimetres, snug but not tight, with the tape parallel to the floor.

How to calculate your body fat, step by step

  1. Measure your neck circumference just below the larynx, tape sloping slightly downward at the front.
  2. Measure your waist circumference at the navel, tape parallel to the floor.
  3. If you're a woman, also measure your hip circumference at its widest point.
  4. Enter your Height, Gender, and all circumference measurements in centimetres.
  5. Click Calculate to see your estimated body fat percentage, category, fat mass and lean mass.

Body fat categories

CategoryMenWomen
Essential fat2-5%10-13%
Athletes6-13%14-20%
Fitness14-17%21-24%
Average18-24%25-31%
Obese25%+32%+

Women's ranges sit higher across every category because some body fat is essential for hormonal and reproductive function. "Fat mass" is your total weight attributable to body fat, and "lean mass" covers muscle, bone, organs and water.

How accurate is this method?

This tape-measure method is a convenient estimate, generally within a few percentage points of clinical results for most people — but it's less accurate than DEXA scans or hydrostatic weighing, which directly measure body composition, and results can shift with inconsistent measuring technique.

Disclaimer: Results are estimates for general awareness only and not medical advice. Please consult a doctor or registered dietitian for personalised health guidance.

Frequently Asked Questions

Women naturally store a larger proportion of body fat around the hips due to differences in typical fat distribution patterns compared to men, who tend to store more fat around the abdomen. The US Navy method's women's formula adds hip circumference to capture this difference, while the men's formula relies on waist and neck alone, which better reflects the typical male fat distribution pattern.

The US Navy tape-measure method is a convenient field estimate, generally within a few percentage points of clinical methods for most people, but it's less accurate than DEXA scans or hydrostatic (underwater) weighing, which directly measure body composition. Accuracy also depends heavily on measuring technique — inconsistent tape tension or placement can shift the result noticeably.

The relationship between circumference measurements and actual body fat percentage isn't linear — a given increase in waist-minus-neck size represents a different amount of added fat depending on your starting size. The logarithmic terms in the US Navy formula were derived by fitting circumference data against measured body fat (via hydrostatic weighing) in the original research, and they compensate for this non-linearity better than a simple ratio would.

Fat mass is the portion of your total body weight made up of body fat, calculated as your weight × body fat percentage. Lean mass is everything else — muscle, bone, organs, water and connective tissue. Two people can have the same total weight but very different fat mass and lean mass, which is why body fat percentage is often more informative than weight or BMI alone.

Measure your neck just below the larynx (Adam's apple), with the tape sloping slightly downward at the front. Measure your waist at the navel, and for women, measure hips at their widest point. All measurements should be taken in centimetres with the tape snug against the skin but not compressing it, and parallel to the floor.

For men: Essential fat is 2-5%, Athletes 6-13%, Fitness 14-17%, Average 18-24%, and Obese is 25%+. For women: Essential fat is 10-13%, Athletes 14-20%, Fitness 21-24%, Average 25-31%, and Obese is 32%+. Women's ranges sit higher across every category because some body fat is essential for hormonal and reproductive function.

It doesn't account for individual variation in fat distribution, ethnicity-based body composition differences, or measurement error from inconsistent tape technique. As a circumference-based estimate, it's inherently less precise than clinical methods like DEXA scans. Results are estimates for general awareness only and not medical advice.
Written and reviewed by Last updated