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Body Fat Percentage Calculator (US Navy Method)

Calculate your body fat percentage using the US Navy method. Get fat mass, lean mass, and body composition classification.

Sources: US Navy Body Composition Assessment — DoD Instruction 1308.3 · ACSM Guidelines for Exercise Testing and Prescription

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How to Calculate Body Fat Percentage

Body fat percentage is a more accurate indicator than BMI for assessing body composition. While BMI only considers weight and height, body fat percentage distinguishes adipose tissue from lean mass (muscles, bones, organs).

The US Navy Method

This calculator uses the US Navy formula, developed by the United States Navy to evaluate the body composition of military personnel. It requires simple measurements with a tape measure:

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

Women: BF% = 495 / (1.29579 - 0.35004 x log10(waist + hips - neck) + 0.22100 x log10(height)) - 450

How to Take Measurements Correctly

For accurate results:

  • Neck: measure at the base, just below the Adam's apple, at the narrowest point
  • Waist: measure at navel height, with your abdomen relaxed (not sucked in)
  • Hips (women only): measure at the widest point, at buttock level

Measure in the morning on an empty stomach, at the same time to track progress over time.

Body Fat Classifications

Reference percentages differ by sex. Men naturally have less fat than women (essential fat is 2-5% for men, 10-13% for women). This is because the female body requires additional fat for hormonal and reproductive functions.

Why Body Fat Matters More Than Weight

Two people can weigh the same but have very different body compositions. An 80 kg athlete with 12% body fat is in excellent condition; a sedentary 80 kg person with 30% body fat has higher cardiovascular risk. The BMI calculation does not capture this difference, which is why body fat percentage is a superior indicator.

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Frequently Asked Questions

How is body fat measured?▼
The US Navy method used in this calculator requires measuring neck, waist, and hip (women only) circumferences with a tape measure. For accurate results, measure in the morning on an empty stomach, standing in a relaxed position. More precise methods include skinfold calipers, bioelectrical impedance analysis (BIA), DEXA scans, and hydrostatic weighing, but these require specialized equipment.
What is the ideal body fat percentage?▼
The ideal percentage depends on sex and age. For men: essential fat 2-5%, athlete 6-13%, fitness 14-17%, acceptable 18-24%, excess >25%. For women: essential fat 10-13%, athlete 14-20%, fitness 21-24%, acceptable 25-31%, excess >32%. Women naturally have more body fat due to hormonal and reproductive functions.
How accurate is the US Navy method?▼
The US Navy method has an accuracy of plus or minus 3-4% compared to hydrostatic weighing, considered the gold standard. It is more precise than BMI for evaluating body composition because it considers body proportions. However, it may be less accurate for people with atypical fat distributions or athletes with significant muscle mass.