Body fat calculator

Your body fat percentage from a tape measure, using the method the US Navy uses for its own fitness standards. No calipers, no scan, about two minutes.

Milo

Sex

Age

Weight (kg)

Height (cm)

Neck (cm)

Waist (cm)

Waist at the navel, neck just below the larynx. Relaxed, not sucked in, tape snug but not tight.

Your body fat will appear here.

How this is worked out

Body fat is worked out from circumference, not weight. Fat sits around the waist, so the gap between your waist and your neck tracks how much you’re carrying, scaled against your height. Women’s fat distributes differently, so the formula adds the hips.

men: 495 / (1.0324 − 0.19077·log10(waist − neck) + 0.15456·log10(height)) − 450

It usually lands within three or four percentage points of a DEXA scan, which is more than good enough to set a protein target or track a direction. Skinfold calipers can beat it, but only in trained hands: most people using calipers on themselves do worse than this.

What matters more than the absolute number is measuring the same way every time. Same time of day, relaxed, tape snug but not compressing. The trend over a month tells you whether a diet is working; a single reading doesn’t.

The number is the easy part

Any calculator can hand you a figure. The hard bit is the next three months: eating roughly to it, noticing when it stops working, and changing it. Milo is a coach you text like a friend. You log what you ate in a sentence, and it learns your patterns, notices when your weight stalls, and adjusts the target from what you actually did rather than from a formula.

See how Milo works

Common questions

How accurate is the tape method?

Typically within three to four percentage points of a DEXA scan. The error is consistent though, which is the useful part: if it reads two points high today it’ll read two points high next month, so the change it shows is real even when the absolute number is slightly off.

Where exactly do I measure?

Waist at the navel, not at the narrowest point and not where your trousers sit. Neck just below the larynx, tape sloping slightly down at the front. Hips, for women, at the widest point of the buttocks. Stand relaxed and breathe out normally: sucking in inflates the result.

Why does it need my height?

Because the same waist measurement means something different on a 160cm frame than a 190cm one. Height is what turns a raw circumference into a proportion.

What's a healthy body fat percentage?

Broadly, 10-20% for men and 18-28% for women covers the healthy range, with athletes lower. But the range is wide and the ends of it suit different people. If you’re inside it and your habits are good, chasing a lower number rarely improves anything that matters.

Other calculators

Lean body mass calculator — How much of your weight isn't fat, and why it matters.
BMI calculator — Your BMI, plus an honest account of what it can't tell you.
Waist-to-height ratio — The one-line check that beats BMI: waist under half your height.
TDEE calculator — How many calories you burn in a day, and what to eat for your goal.
Calorie deficit calculator — How long a given deficit takes to reach your goal weight.

These are estimates from population averages, not measurements of you. Individual metabolism varies by roughly ±10% around any formula. Nothing here is medical advice — if you have a health condition, are pregnant, or are under 18, talk to a healthcare professional before changing how you eat or train.