Bra Size Calculator

US, UK, European and French sizes from two measurements.

Technique moves the reading more than most people expect: a waist taped at the navel and one taped at the narrowest point can differ by two inches, and impedance scales shift with hydration. Consistency of method matters more than the absolute number on any single day.

Body measurements in the United States are read against published reference tables: BMI categories from the CDC, body-fat ranges from the American Council on Exercise, and circumference standards used by the Army and Navy. BMI divides weight by height squared and cannot separate muscle from fat, so a lean, heavily built person can read as overweight.

Waist measurement and body-fat estimates fill in what the index alone misses.

These scales were built on population averages, so a single reading says more about where you sit against a table than about your own health.

Fat-free mass, hydration and time of day all move a reading, and a measurement taken after a meal or a workout reads differently from one taken fasted. Trends over weeks, taken the same way, describe a body; a single figure describes a moment.

Bra Size Calculator sits with the rest of the library's everyday work, and it rests on the same body-measurement arithmetic the way a manufacturer's label or a timetable does. Its answer is only as good as the assumptions standing behind it.

The quantities it works from — measurements in, underbust, snug and bust at the fullest point — are the ones a real body-measurement question actually turns on, and each carries a convention of its own, set out below.

Everyday arithmetic in the United States carries conventions that are easy to miss: dates run month before day, distances and weights follow customary units, and prices are quoted before tax. Those conventions make a surprising share of daily sums come out differently from the same question asked elsewhere.

The figures in this section follow American practice unless the subject itself is international.