What Are Bra Sister Sizes?
Sister sizes are groups of bra sizes that share the same cup volume but have different band sizes. Understanding sister sizes can be incredibly helpful when shopping for bras.
How Sister Sizes Work
The relationship is simple: when you go up one band size, you go down one cup size (and vice versa). This keeps the overall cup volume the same.
Example:
If your size is 34C, your sister sizes are:
- 32D — Tighter band, same cup volume
- 36B — Looser band, same cup volume
When to Use Sister Sizes
- Your exact size is sold out
- A brand’s sizing runs large or small
- You’re between two band sizes
- You want to adjust the fit slightly
Complete Sister Size Chart
| -2 Band (Tighter) | Your Size | +2 Band (Looser) |
|---|---|---|
| 28C | 30B | 32A |
| 28D | 30C | 32B |
| 30D | 32C | 34B |
| 30DD | 32D | 34C |
| 32DD | 34D | 36C |
| 32DDD | 34DD | 36D |
| 34DD | 36D | 38C |
| 34DDD | 36DD | 38D |
Use our Sister Size Calculator to find your specific sister sizes instantly.