The US Navy method estimates body fat from a few tape measurements. It is less accurate than a DEXA scan, but it needs nothing but a tape measure and it tracks change over time well - which for most purposes matters more than the absolute number being exactly right.
Neck: just below the larynx, tape sloping slightly downward at the front. Waist: at the navel for men, at the narrowest point for women. Hips: at the widest point. Stand relaxed, breathe out normally, and keep the tape snug without compressing the skin. Measure at the same time of day each time - abdominal measurements drift by a centimetre or more between morning and evening.
The Navy formula lands within about 3 to 4 percentage points of a DEXA scan, and further out at the extremes. That sounds poor, and for a one-off number it is. Its value is consistency: measured the same way each week, the trend is reliable even when the absolute figure is not. Tracking direction is usually what you actually want.
BMI cannot tell muscle from fat, so two people of identical height and weight score identically regardless of composition. Body fat percentage separates them. This is why a muscular athlete gets flagged as overweight by BMI and looks entirely unremarkable here.
Some body fat is structural - it cushions organs and is required for hormone production. Roughly 3 to 5% for men and 10 to 13% for women is the floor. Sustained levels below that carry real consequences, particularly for hormonal and bone health.
Neck just below the larynx, sloping slightly downward at the front. Waist at the navel for men, at the narrowest point for women. Hips at the widest point. Measure relaxed, not holding your breath in, and keep the tape snug but not compressing the skin.
Typically within 3 to 4 percentage points of a DEXA scan, and it can be further out for very lean or very heavy people. Its real strength is consistency: measured the same way each time, the trend is reliable even when the absolute figure is not.
Because it distinguishes muscle from fat, which BMI cannot. Two people of identical height and weight have identical BMI whether the difference is muscle or fat. Body fat percentage separates them, which is why a muscular athlete flagged as overweight by BMI usually looks entirely normal here.
Steuervergleich Kanton Zürich — Gemeindesteuern vergleichen (Deutsch)