36DD 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 34E

Choose 34E if the 36 band rides up. In UK lettering the cup above DD is E. American size charts show this size as 34DDD, which is the same thing under another name.

When to choose 38D

Choose 38D if the 36 band is too tight and the cups fit. The letter drops from DD to D, and the cup volume stays the same.

What a 36DD measures

All three sizes are designed around a bust of about 41 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.

This family is where UK and US charts first disagree, so check which country's chart you are reading before you rely on it.

If neither sister size works

Sister sizes only help when the cup volume is already right. If you spill out of a 36DD or the cups gape, keep the 36 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 36DD?

34E on a firmer band and 38D on a looser band. Both have the same cup volume as a 36DD.

Is a 34E the same as a 36DD?

The cups hold the same volume. The 34E has a band one size smaller, so it fits more firmly around the ribcage.

Can I wear a 40C if I am a 36DD?

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.