A C cup means your bust measures about 3 inches more than your band. It isn’t a fixed volume: a 32C and a 40C are both C cups, but the 40C holds far more because the cup grows with the band. US, UK, EU and Australian sizing all use the letter C.
| Band 34 | Underbust over 32 and up to 34 inches (81–86 cm). We round your underbust up to the next even number. |
|---|---|
| Cup C | Bust about 3 inches bigger than the band: roughly 36½ to 37½ inches (93–95 cm) around the fullest part. |
| Sister sizes | 32D (tighter band) and 36B (looser band). Full diagonal: 28DDD (UK 28E), 30DD, 32D, 34C, 36B, 38A, 40AA. |
| Same size abroad | UK 34C · EU 75C · French 90C · Australia / NZ 12C |
Brands measure differently, and some US brands add inches to the band. Use these numbers as a starting point, then check the fit. Calculate your own size · See every sister size · Convert another size
C cup sizes across bands
| Size | Underbust (in) | Bust (approx. in) | Sister sizes |
|---|---|---|---|
| 30C | 28–30 | 33 | 28D, 32B |
| 32C | 30–32 | 35 | 30D, 34B |
| 34C | 32–34 | 37 | 32D, 36B |
| 36C | 34–36 | 39 | 34D, 38B |
| 38C | 36–38 | 41 | 36D, 40B |
| 40C | 38–40 | 43 | 38D, 42B |
| 42C | 40–42 | 45 | 40D, 44B |
These follow our measuring method: underbust rounded up to the next even number for the band, then one inch per cup. Some US brands still add inches to the band, so their charts can differ. Our guides to 32C, 34C and 36C cover the most common C sizes in detail.
Is a C cup big?
Not on its own. Because cup volume grows with the band, a 30C has about the same volume as a 32B or 28D, while a 40C matches a 38D or 42B. Brastop’s sister size guide explains this diagonal: each step down in band and up in cup keeps the volume the same.
In everyday terms, many people would call a 34C or 36C a “medium” bust. Our guide to what bra size is considered big explains why the band matters as much as the letter.
How to know you’re a C cup
- Measure snugly under your bust and round up to the next even number. That’s your band.
- Measure loosely around the fullest part of your bust.
- Subtract the band from the bust. 3 inches means a C cup.
Then check the fit. If the cups gape, try a B. If you spill over the top or the wire sits on your breast tissue at the side, try a D. The bra size calculator does the math for you.
Signs your C cup isn’t right
- Band rides up but cups fit: go down a band and up a cup, like 34C to 32D.
- Cups wrinkle at the top: try a B, or a balconette that suits less upper fullness.
- Spilling at the sides: try a D, or a full cup with taller side wings.
Shop C cup bras by size
Affiliate links-
32C bras
Smaller band, so check the size range before you order.
Search Amazon for 32c bras (opens in a new tab, affiliate link) -
34C bras
One of the most widely stocked sizes.
Search Amazon for 34c bras (opens in a new tab, affiliate link) -
36C bras
Widely stocked; compare full cup and T-shirt styles.
Search Amazon for 36c bras (opens in a new tab, affiliate link) -
38C and up
Look for wider bands with three or more hooks.
Search Amazon for 38c and up (opens in a new tab, affiliate link)
Results are Amazon’s, not our picks. Check the size range, the return policy and the features above before you buy.
C cup vs B cup vs D cup
Each cup step adds about an inch at the bust on the same band. So on a 34 band, B is about 36 inches, C is about 37 and D is about 38. Our B cup and D cup guides cover the neighboring sizes, and the bra size chart shows the whole range.
