34DD 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 32E

Choose 32E if the 34 band is loose. E is one step above DD in the UK. On a European label this size would read 70F, and on an American one 32DDD.

When to choose 36D

Choose 36D if the band is too tight and the cups are right.

What a 34DD measures

All three sizes are designed around a bust of about 39 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 34DD is frequently the size people are wearing when the size that fits them is a 32E or a 32F: a band too loose and a cup a little too small. If your 34DD rides up and the centre panel does not sit flat, try 32E and then 32F.

If neither sister size works

Sister sizes only help when the cup volume is already right. If you spill out of a 34DD or the cups gape, keep the 34 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 34DD?

32E on a firmer band and 36D on a looser band. Both have the same cup volume as a 34DD.

Is a 32E the same as a 34DD?

The cups hold the same volume. The 32E has a band one size smaller, so it fits more firmly around the ribcage.

Can I wear a 38C if I am a 34DD?

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.