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Quick guide

What This Calculator Does

Weight and BMI describe a height-to-weight ratio; they do not directly reveal how much of body weight is fat. This page gives a rough home estimate from two different equation families: one using BMI, age, and sex, and another using height and circumference measurements. It then shows both estimates, their arithmetic average, and a page reference category.

The page is most useful when adults repeat the measurements in the same way and watch the direction over weeks or months. It is not a DEXA, Bod Pod, hydrostatic-weighing, skinfold, or other professional body-composition test, and one result cannot diagnose obesity, metabolic risk, or athletic ability.

When to Use It

  • You want a body-composition starting estimate rather than weight alone.
  • You can measure waist, neck, and, in female mode, hip circumference consistently.
  • You want to compare an age/BMI estimate with a circumference estimate instead of trusting one number.
  • You are prepared to keep timing, landmarks, and measuring habits consistent for trend tracking.

Inputs Explained

Sex

The sex selection changes the BMI/age coefficients, page category thresholds, and circumference equation; female mode also shows and uses hip circumference. It is a formula input label, not a complete model of gender identity, hormone status, or body variation.

Age

The control accepts 18–100 years. Age enters the BMI/age estimate but not the circumference equation. Minors should not apply this adult page’s inputs or categories directly.

Read the full guide

Frequently Asked Questions

Which formulas does this page use?

It uses an age/BMI/sex equation and a Navy-style circumference equation using waist minus neck for men and waist plus hip minus neck for women, then shows the arithmetic average.

Why can the two estimates differ?

The methods use different body inputs and assumptions; landmarks, breathing, tape tension, body shape, and formula units can all change the difference.

Is the average a professional test result?

No. It is a page-level arithmetic combination for repeat tracking and trend comparison, not a substitute for DEXA, Bod Pod, hydrostatic weighing, or professional body-composition assessment.

Can the page category diagnose health or obesity?

No. It is a page reference label, not a diagnosis, athletic standard, or fat-loss prescription; special situations and health concerns need a clinician or registered dietitian.

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Body Fat Calculator

Compare an age/BMI estimate with a Navy-style circumference estimate from adult measurements, then view an average reference; results are for trend tracking, not body-composition testing or diagnosis.

Body data

Choose sex first, then enter age, height, weight, and circumferences. The page compares an age/BMI equation with a Navy-style circumference equation as an adult trend baseline.

Use an example
Sex
Basic data
cm
kg
Circumference data
cm
cm

Body fat result

The average is only an arithmetic combination of the age/BMI and Navy-style circumference estimates; it is not a measured body-fat value or diagnosis.

Ready to calculate

After calculation, this panel shows average body fat, method split, and category.

This page is a rough adult estimate using fixed equations and tape measurements. It does not model muscle mass, fat distribution, illness, medication, pregnancy, or training status. Landmark choice, breathing, tape tension, and body shape can change the result; athletes, pregnancy/breastfeeding, eating disorders, minors, or anyone with health concerns should not make diet or medical decisions from this category alone—ask a clinician or registered dietitian.

Measurement guide

Measure horizontally with a soft tape while standing naturally. Do not pull too tight.

Waist

Waist

Stand naturally and measure at a repeatable waist landmark. Keep your abdomen relaxed and the tape snug without compressing skin.

Neck

Neck

Place the tape near the base of the neck below the larynx, keep it level, and relax the shoulders.

Hip

Hip

Female mode requires a hip measurement around the widest part of the hips; other body-fat methods are not calculated here.