This calculator estimates body fat using the U.S. Navy circumference method. It works on a different principle than bioelectrical impedance analysis (BIA) devices like InBody, so results may differ. For a precise body composition analysis, an InBody or similar BIA measurement is recommended.
This calculator estimates body fat using the U.S. Navy circumference method. It works on a different principle than bioelectrical impedance analysis (BIA) devices like InBody, so results may differ. For a precise body composition analysis, an InBody or similar BIA measurement is recommended.
What is the US Navy body fat method?
The US Navy method estimates body fat percentage from a few circumference measurements instead of expensive equipment. It was developed by Hodgdon and Beckett at the Naval Health Research Center in 1984 and remains widely used because it needs only a measuring tape.
Male: %BF = 495 / (1.0324 − 0.19077×log₁₀(waist−neck) + 0.15456×log₁₀(height)) − 450
Female: %BF = 495 / (1.29579 − 0.35004×log₁₀(waist+hip−neck) + 0.22100×log₁₀(height)) − 450
ACE body fat categories
| Category | Men | Women |
|---|
| Essential fat | 2–5% | 10–13% |
| Athletes | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Obese | 25%+ | 32%+ |
Good to know
Results depend on measurement technique: measure your waist at the navel and your neck just below the larynx, without pulling the tape tight. This is a screening estimate, not a diagnosis — consult a healthcare professional for a full body composition assessment.
Skeletal muscle mass cannot be calculated from this method — it is an InBody-specific metric derived from bioelectrical impedance, not circumference measurements.
How do I calculate body fat percentage (US Navy method)?
To estimate body fat using the US Navy method, measure your waist, neck (and hip if you are a woman) in centimeters, then plug them into the Hodgdon & Beckett regression formula along with your height. Example: a 178 cm man with a 38 cm neck and 90 cm waist has (waist − neck) = 52; his body fat works out to 495 / (1.0324 − 0.19077×log10(52) + 0.15456×log10(178)) − 450 = 20.1%, which falls in the ACE 'Average' category.
Steps to calculate body fat with the Navy method
- Measure waist at the navel and neck just below the larynx, in centimeters (women also measure hip at its widest point).
- For men, calculate (waist − neck). For women, calculate (waist + hip − neck).
- Take the base-10 logarithm (log10) of that difference and of height in centimeters.
- Plug the values into the men's or women's regression formula to solve for body fat percentage.
- Round to one decimal place and compare the result against the ACE category table.
US Navy body fat formula
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.
- waist = waist circumference in cm, measured at the navel
- neck = neck circumference in cm, measured just below the larynx
- hip = hip circumference in cm at the widest point (women only)
- height = height in cm
- log10 = base-10 logarithm
Quick body fat answers
What is the body fat percentage of a 178 cm man with a 38 cm neck and 90 cm waist?
His body fat is 20.1% (495 / (1.0324 − 0.19077×log10(52) + 0.15456×log10(178)) − 450), which falls in the ACE 'Average' category for men.
What is the body fat percentage of a 163 cm woman with a 32 cm neck, 74 cm waist, and 96 cm hip?
Her body fat is 28.0% (495 / (1.29579 − 0.35004×log10(138) + 0.22100×log10(163)) − 450), in the ACE 'Average' category for women.
What is the body fat percentage of a 175 cm man with a 36 cm neck and 75 cm waist?
His body fat is 10.2%, which falls in the ACE 'Athletes' category for men.
What is the body fat percentage of a 185 cm man with a 40 cm neck and 105 cm waist?
His body fat is 27.4%, which falls in the ACE 'Obese' category for men.
What is the body fat percentage of a 170 cm woman with a 30 cm neck, 65 cm waist, and 85 cm hip?
Her body fat is 16.6%, which falls in the ACE 'Athletes' category for women.
Is 25% body fat high for a man?
Yes. On the ACE scale, 25% or higher is classified as obese for men; 18-24% is average, and 14-17% is the fitness range.
What body fat percentage counts as 'Athletes' for women?
14% to 20%, according to the ACE categories used by this calculator; men's athlete range is lower, at 6% to 13%, reflecting essential fat differences between sexes.
Why does the formula use hip measurement for women but not men?
Hodgdon and Beckett's 1984 regression found that adding hip circumference improved accuracy for women's typically different fat distribution, while for men waist and neck alone gave a good estimate. This is why the two formulas differ.
Example body fat results
| Sex | Height | Neck | Waist | Hip | Body fat % | ACE category |
|---|
| Male | 178 cm | 38 cm | 90 cm | – | 20.1% | Average |
| Male | 175 cm | 36 cm | 75 cm | – | 10.2% | Athletes |
| Male | 185 cm | 40 cm | 105 cm | – | 27.4% | Obese |
| Female | 163 cm | 32 cm | 74 cm | 96 cm | 28.0% | Average |
| Female | 170 cm | 30 cm | 65 cm | 85 cm | 16.6% | Athletes |
Frequently asked questions
How accurate is the US Navy body fat method?
Validation studies show it typically comes within about 3-4 percentage points of DEXA (the imaging-based reference standard) for most adults, which is why it has been the US military's field method since 1984. Accuracy drops for people with atypical fat distribution or very high or very low body fat.
Why is my result different from my InBody number?
InBody and similar devices use bioelectrical impedance analysis (BIA), which sends a small electrical current through your body and estimates composition from the resistance. The Navy method instead uses a regression formula based on circumference measurements. The two principles can disagree by several percentage points, especially at the high or low ends.
Where exactly should I measure waist and neck?
Measure waist circumference at the navel, standing relaxed without pulling in your stomach. Measure neck circumference just below the larynx (Adam's apple), and hip circumference (women only) at the widest point of the hips. Keep the tape snug but not compressing the skin.
What are the ACE body fat categories?
The American Council on Exercise defines five ranges: essential fat (2-5% men, 10-13% women), athletes (6-13% men, 14-20% women), fitness (14-17% men, 21-24% women), average (18-24% men, 25-31% women), and obese (25%+ men, 32%+ women).
Can this calculator give me my skeletal muscle mass?
No. Skeletal muscle mass is calculated from bioelectrical impedance data on devices like InBody, not from circumference measurements. The Navy method only estimates total body fat percentage.
This is a screening estimate based on the US Navy circumference regression formula (Hodgdon & Beckett, 1984). It does not directly measure body fat and can be less accurate for people with atypical fat distribution, very muscular or very lean individuals, or those outside the population the formula was validated on. It differs in principle from bioelectrical impedance analysis (BIA) devices like InBody. Consult a healthcare or fitness professional, or a DEXA/BIA measurement, for a precise body composition assessment.
Sources: calculator.net – Body Fat Calculator, Hodgdon & Beckett, Naval Health Research Center Report 84-11 (1984), ACE – Percent Body Fat Calculator & Categories