30E Sister Sizes

The sizes in bold are the ones to use. The outer two share the cup volume in theory, but are proportioned for a noticeably different frame.

When to choose 28F

Choose 28F if the 30 band is loose. 28 bands are made by a limited number of full-bust brands and are rarely found on the high street, so expect to buy from a specialist or online.

When to choose 32DD

Choose 32DD if the 30 band is too firm, or simply because it is far easier to find. If the 32 band then rides up, the 30 was right and it is worth seeking out.

What a 30E measures

All three sizes are designed around a bust of about 36 inches. The difference is how much of that total is ribcage and how much is breast, which is why the band changes and the cup letter moves the other way.

A 30E is a small-band, fuller-cup size that many shops do not stock. People who need it are often sold a 34C instead, which has a band four inches too long and a cup that is smaller.

If neither sister size works

Sister sizes only help when the cup volume is already right. If you spill out of a 30E or the cups gape, keep the 30 band and change the cup letter. If you are unsure which problem you have, when to sister size up or down will help you decide, and the calculator will give you a fresh starting size from your measurements.

Frequently asked questions

What is the sister size of a 30E?

28F on a firmer band and 32DD on a looser band. Both have the same cup volume as a 30E.

Is a 28F the same as a 30E?

The cups hold the same volume. The 28F has a band one size smaller, so it fits more firmly around the ribcage.

Can I wear a 34D if I am a 30E?

That is two steps away. The cup volume is the same on paper, but the wires, straps and proportions are made for a larger frame, and the band will be four inches longer. It is unlikely to support you well.