Free tool
Body fat calculator
A more useful number than BMI, because it separates muscle from fat. This uses the US Navy circumference method — a tape measure and three measurements, no calipers needed.
How to measure
Neck — just below the larynx, tape sloping slightly down at the front. Do not flex.
Waist — at the navel for men, at the narrowest point for women. Relaxed, at the end of a normal breath out. Do not suck in.
Hip — women only, at the widest point.
Measure first thing in the morning, before eating, and keep the same routine every time. The absolute number matters less than the direction it moves over a month.
Reference
What the ranges mean.
Women carry more essential fat than men — it is physiological, not a fitness gap. Anything at or below the essential band is not a target; it is a medical concern.
Expect the Navy method to be within roughly 3–4 percentage points of a DEXA scan for most people. It is far better at tracking change than at nailing an absolute figure.
| Category | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athlete | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Above average | 25%+ | 32%+ |
Frequently asked questions
How accurate is the US Navy method?
Usually within 3–4 percentage points of a DEXA scan. It is less accurate at the extremes — very lean or very heavy — but it is free, repeatable and good at showing direction over time, which is what actually matters.
Why does it ask for my waist rather than my weight?
Because circumference is what correlates with fat distribution. Weight cannot distinguish muscle from fat; a waist measurement largely can. Weight is only used here to convert the percentage into fat and lean mass.
My result looks wrong.
Check that everything is in centimetres and that waist is larger than neck. The formula breaks down if the difference between them is very small, in which case the calculator will tell you to re-measure rather than print a nonsense figure.
How fast can body fat realistically drop?
Roughly half a percentage point to one point a month at a sensible deficit. Anything much faster usually means muscle is going too. Use the calorie deficit calculator to set a rate you can hold.
Next step
Measuring is easy. Logging is the hard part.
Free to start on iPhone and Android.
