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US Navy Method · ACSM Categories · Updated 2026

Body Fat Calculator

Calculate your body fat percentage without specialised scales or bioimpedance using the US Navy method. All you need is a tape measure. Free, no sign-up.

Tape measure only US Navy Method ACSM Categories 100% private

How to measure: Neck: below the larynx, perpendicular. Waist: at navel level, horizontal.

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Enter your measurements to see the result

You will get your body fat percentage, ACSM category, fat mass and lean mass (if you enter your weight).

Complete guide

All About Body Fat

Body fat percentage is one of the most accurate indicators of metabolic health and body composition. We explain how to interpret it.

What is body fat %?

Body fat percentage indicates what fraction of your total weight corresponds to adipose tissue. The rest is lean mass: muscle, bone, water and organs. It is a much more precise health indicator than BMI, as it directly distinguishes between fat and muscle.

  • • Predictor of metabolic risk
  • • Useful for diet and training tracking
  • • Differs between men and women due to biology

US Navy Method: how to measure

The US Navy method estimates body fat % with just a tape measure, with an error of ±3–4% compared to DEXA (gold standard). You only need three measurements for men and four for women.

Men:

Height · Neck · Waist (navel)

Women:

Height · Neck · Waist (narrowest) · Hip (widest)

ACSM categories explained

The American College of Sports Medicine (ACSM) establishes the most clinically used categories for body fat percentage.

Essential — functional minimum
Athletic / Fit — optimal
Average — acceptable
Fat overweight — increased risk
Obese — high risk

Frequently asked questions

All About Body Fat

Evidence-based answers about body fat percentage, measurement methods and how to improve your body composition.

According to ACSM categories, the reference ranges are:

Men

Essential: <6%

Athletic: 6–13%

Fit: 14–17%

Average: 18–24%

Overweight: 25–31%

Obese: >32%

Women

Essential: <14%

Athletic: 14–20%

Fit: 21–24%

Average: 25–31%

Overweight: 32–38%

Obese: >39%

Women physiologically have a higher body fat percentage than men due to hormonal and reproductive requirements.

The US Navy method uses body circumference measurements to estimate fat. The formulas are:

For men:

% Fat = 495 / (1.0324 − 0.19077 × log(waist − neck) + 0.15456 × log(height)) − 450

For women:

% Fat = 495 / (1.29579 − 0.35004 × log(waist + hip − neck) + 0.22100 × log(height)) − 450

Accuracy is ±3–4% compared to DEXA (Dual Energy X-ray Absorptiometry), which is the gold standard. It is sufficiently accurate for personal tracking.

For athletes or people with a lot of muscle mass, body fat percentage is clearly superior to BMI. A bodybuilder may have a BMI of 30 (obesity) with only 8% body fat: BMI would be completely misleading. However, for the general sedentary population, BMI remains a good population-level predictor of cardiovascular risk. The ideal approach is to combine both metrics with waist circumference for a complete assessment.

To lose body fat sustainably without losing muscle:

  • 1. Moderate caloric deficit: 300–500 kcal/day below your total expenditure. Larger deficits accelerate muscle loss.
  • 2. High protein intake: 1.6–2.2 g per kg of weight to preserve muscle mass during the deficit.
  • 3. Strength training: Maintains and even increases muscle mass during fat loss.
  • 4. Complementary cardio: 150+ minutes per week of moderate intensity to increase caloric expenditure.
  • 5. Quality sleep: 7–9 hours. Sleep deprivation increases cortisol and promotes abdominal fat accumulation.

A sustainable loss is 0.5–1 kg/week, equivalent to losing 0.3–0.7% body fat per week depending on weight.

Subcutaneous fat

  • • Under the skin (hips, thighs, arms)
  • • Visible and palpable
  • • Lower metabolic risk
  • • Harder to lose in women

Visceral fat

  • • Surrounds internal organs
  • • Not externally visible
  • • Highly inflammatory
  • • Predictor of cardiovascular risk

Visceral fat is metabolically active and releases fatty acids directly to the liver, causing insulin resistance, systemic inflammation and increased risk of type 2 diabetes, hypertension and cardiovascular disease. Waist circumference is the best clinical indicator of visceral fat (risk if >102 cm in men or >88 cm in women).

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