MMaxTools

Body Fat Calculator

Estimate body fat percentage from tape measurements — no special equipment.

The Body Fat Calculator estimates your body fat percentage from simple tape measurements using the US Navy circumference method — the same approach used by many trainers and health programs because it needs nothing but a measuring tape.

For men the inputs are height, waist and neck; for women, height, waist, neck and hip. The formulas were developed from hydrostatic weighing studies and typically land within a few percentage points of laboratory methods for average body shapes — enough to track your trend month to month.

Body fat percentage is a better health and fitness metric than BMI for active people because it distinguishes fat from muscle. The result comes with a category band (athletic, fitness, average…) so the number has context. Educational estimate only — DEXA scans are the reference standard.

Estimated body fat

17.96%

US Navy circumference method

Category

Above average

population ranges

Navy-method estimates come from circumference formulas with ±3–4% typical error; DEXA or hydrostatic weighing are the reference methods. Track trends, not single readings.

How to use the Body Fat Calculator

  1. Choose your sex — the required measurements differ.
  2. Measure height, waist (at the navel) and neck, plus hip for women.
  3. Enter all measurements in centimeters.
  4. Read your estimated body fat percentage and category.
  5. Re-measure monthly under the same conditions to track trends.

Frequently asked questions

How accurate is the Navy method?

Studies show typical error of roughly ±3–4% compared with reference methods for average body shapes. It is most useful for tracking change over time rather than as an absolute lab-grade number.

Where exactly should I measure?

Waist at the navel with relaxed stomach, neck just below the larynx, and hips at the widest point. Use a flexible tape, keep it level, and measure at the same time of day for comparable results.

What body fat percentage is healthy?

Essential fat is roughly 2–5% for men and 10–13% for women; athletic ranges are about 6–13% (men) and 14–20% (women), with average adults around 18–24% (men) and 25–31% (women). Below essential levels is unhealthy for both sexes.