The EN 13402 method
The European clothing standard EN 13402 labels a bra with two numbers taken from body measurements. The band is the underbust girth rounded to the nearest 5 cm (60, 65, 70 … 125). The cup letter comes from the difference between bust girth and underbust girth, in 2 cm steps.
If you measure in inches the calculator converts with 1 in = 2.54 cm before applying the standard.
| Cup | Bust − underbust |
|---|---|
| AA | 10–12 cm |
| A | 12–14 cm |
| B | 14–16 cm |
| C | 16–18 cm |
| D | 18–20 cm |
| E | 20–22 cm |
| F | 22–24 cm |
| G | 24–26 cm |
| H | 26–28 cm |
Worked example
An underbust of 89 cm and a bust of 108 cm: the band is 89 rounded to the nearest 5, which is 90; the difference is 108 − 89 = 19 cm, in the D range. The size is 90D.
With the calculator's default 76 cm and 92 cm, the band is 75 and the 16 cm difference is a C, so 75C.
Why your size may differ in the shop
UK, US, French and Australian labels use different band numbers and cup letters from EN 13402, and brands and styles fit differently even within one system. Use the result as a starting point and try on nearby sizes.
Measure standing straight and breathing normally, keeping the tape level and snug but not tight, ideally over a non-padded bra.