Estimate body fat from Navy circumferences

You enter formula sex, height, waist, neck, and hips if the female equation applies. The tool converts centimeters to inches (divide by 2.54) because the original papers are in inches, then applies log10. Men: waist and neck. Women: waist, hips, and neck. A waist smaller than the neck (men) or an inconsistent combination (women) is rejected. The result can print low or high depending on tape placement: that is not a reason to invent a “DXA correction.”

Hommes : % ≈ 495 / (1,0324 − 0,19077 log10(taille_po − cou_po) + 0,15456 log10(hauteur_po)) − 450

Femmes : % ≈ 495 / (1,29579 − 0,35004 log10(taille_po + hanches_po − cou_po) + 0,221 log10(hauteur_po)) − 450

These Naval Health Research Center reports predict a percent from circumferences and height, for 1980s military populations. The method is widely reused as “U.S. Navy body fat.” It does not equal DXA, hydrostatic weighing, or a BOD POD. We do not publish an invented standard error. “Essential / athlete / fitness” bins seen on other sites are not in our cited sources: we therefore do not label the percent beyond the raw number.

Sex

Switches between the two 1984 reports. It is not a sociological gender field.

Height

Height enters as log10 in both formulas: measure it as carefully as for BMI.

Waist

Tape placement (navel vs smallest waist) is the main day-to-day gap.

Neck

A crooked or too-high tape moves the logarithm as much as a real composition change.

Hips

Largest hip circumference, horizontal. Required if sex = female. Ignored by the male formula.

Assumptions

• Measurements taken in comparable conditions (same time of day, same tape tension).
• Anatomy compatible with “Navy” circumferences (no malformation, not pregnancy).
• Inch = 2.54 cm exactly.

Limits

• Not DXA, not a scan, not scale impedance.
• Calibrated on 1984 military cohorts, not your clinic today.
• Sensitive to tape technique and gut contents.
• No “athlete” classes displayed: we do not have that source here.

Use the percent to follow a trend if you always measure in the same place, not to post a “stage body fat.” BMI is another number (kg/m²): the two can tell different stories, and neither is a diagnosis. A violent week-to-week swing often flags the tape, not 4 points of fat gone.

• Measuring waist after a meal or while sucking in.

  The formula believes the circumference you typed. Suck in, the percent drops on screen, not in adipose tissue.

• Skipping hips for a woman.

  The 84-29 formula needs them. Without hips, the calculation is refused rather than borrowing the male formula.

• Comparing this % to a cheap scale’s impedance as if they were interchangeable.

  Two estimators, two biases. Neither is DXA.

• BMI calculatorBody mass index is weight in kg divided by height in meters squared. Labels use adult WHO cut-offs. That is not an obesity diagnosis by itself, and it is not a child BMI.
• Reference weightThe featured result is the kilogram interval that matches BMI 18.5 to 24.9 for your height. Devine, Robinson, and Miller are historical conventions, not a weight “to aim at.”

Written by Rédaction HexaCalc (editorial team). Content last updated: August 25, 2026. No third-party medical or financial review is claimed.

• Hodgdon JA, Beckett MB — Prediction of percent body fat for U.S. Navy men from body circumferences and height (1984) — Naval Health Research Center, Report No. 84-11
• Hodgdon JA, Beckett MB — Prediction of percent body fat for U.S. Navy women from body circumferences and height (1984) — Naval Health Research Center, Report No. 84-29