Cherry SizeSister sizes: one cup volume, three sizes
A sister size is a bra size with the same cup volume but a different band length. Every size has two: go one band down and one cup letter up, or one band up and one cup letter down. 75C, 70D and 80B all hold the same volume — they differ only in how tight the band is.
The rule
- Band too tight? Take the sister size up: 75C → 80B.
- Band riding up, straps slipping? Take the sister size down: 75C → 70D.
- The cup letter changes, the cup volume doesn't.
Find your sister sizes
| Band down (tighter) | Your size | Band up (looser) |
|---|---|---|
| 30C | 32B | 34A |
| 30D | 32C | 34B |
| 30DD | 32D | 34C |
| 30DDD | 32DD | 34D |
| 32C | 34B | 36A |
| 32D | 34C | 36B |
| 32DD | 34D | 36C |
| 32DDD | 34DD | 36D |
| 34C | 36B | 38A |
| 34D | 36C | 38B |
| 34DD | 36D | 38C |
| 34DDD | 36DD | 38D |
| 36C | 38B | 40A |
| 36D | 38C | 40B |
| 36DD | 38D | 40C |
| 36DDD | 38DD | 40D |
Why sister sizes matter when you shop
Two situations call for a sister size. First, fit: if a bra is perfect in the cup but wrong in the band, the sister size fixes the band while keeping the volume. Second, availability: many brands don't produce every combination, so knowing your sisters instantly doubles your options in the sale rack. The Cherry Size app shows your sister sizes automatically with every estimate — and tells you which one to prefer at each of 632 brands.
Your size, everywhere you shop
Cherry Size keeps your measurements on your iPhone, translates them into 632 brands, tracks changes through pregnancy, nursing or weight shifts — and never uploads a thing.
Download on the App Store