Body Fat Calculator
Body-fat percentage from a tape measure — the US Navy circumference method: height, neck and waist, plus hips for women. With a weight it splits fat mass from lean mass, and the ACE bands say what the number means. No calipers, no scan, nothing uploaded.
Why circumference works at all
Fat accumulates where the tape goes — the waist above all — while the neck tracks lean frame size. The Navy fitted logarithms of those circumferences against underwater weighing on thousands of service members, and the result predicts hydrostatic body fat remarkably well for something a person can do alone in two minutes.
The split into fat and lean mass is where the number becomes useful: a cut that costs 4 kg of which 3 were lean is a failed cut, and only the split shows it.
Frequently asked questions
How accurate is the tape method?
Within about 3 to 4 percentage points of a DEXA scan for most bodies — worse at the extremes of leanness. That is honest enough for tracking direction over months, which is the job: measure the same way each time, and the trend is more trustworthy than any single reading.
Where exactly do I put the tape?
Neck: just below the larynx, tape sloping slightly down to the front. Waist: at the navel for men, at the narrowest point for women, relaxed — measuring sucked-in is measuring a wish. Hips: at the widest point. Snug tape, no compression, same time of day.
Why do women measure hips and men not?
Because fat distributes differently: the female formula was fitted with hip circumference as a third term and loses accuracy without it. The two equations also carry different constants — the same tape numbers mean different percentages by sex, which the category bands reflect too.
What is a healthy percentage?
The ACE bands this page shows: for men roughly 6–13% athletic, 14–17% fit, 18–24% average; for women 14–20%, 21–24%, 25–31% — the difference is essential fat, which women's physiology requires. Below essential fat is a medical problem, not an achievement.
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- Ideal Weight CalculatorIdeal body weight by Devine, Robinson, Miller and Hamwi — the formulas medicine actually cites — plus the healthy-BMI weight band for your height.