Question 1

What are sister bra sizes?

Accepted Answer

Sister sizes are bra sizes with the same cup volume but different band lengths. If you go down a band size, go up a cup size; if you go up a band size, go down a cup size.

Question 2

How do I find sister sizes?

Accepted Answer

Use the rule: down band → up cup; up band → down cup. Try one or two steps. Our Sister Sizes Finder suggests options for US/UK/EU/JP systems.

Question 3

Do sister sizes work across US/UK/EU/JP?

Accepted Answer

The concept is the same, but cup letters differ by system. Use sister sizes within one system, then convert if needed.