A, B and C measurements by band
Each cell is the bust measurement that size is built for.
| Band | A cup | B cup | C cup |
|---|---|---|---|
| 30 | 31 in (79 cm) | 32 in (81 cm) | 33 in (84 cm) |
| 32 | 33 in (84 cm) | 34 in (86 cm) | 35 in (89 cm) |
| 34 | 35 in (89 cm) | 36 in (91 cm) | 37 in (94 cm) |
| 36 | 37 in (94 cm) | 38 in (97 cm) | 39 in (99 cm) |
| 38 | 39 in (99 cm) | 40 in (102 cm) | 41 in (104 cm) |
These three letters are identical in UK, US, European, French and Australian sizing. Only the band number changes between systems.
The letter means little without the band
Look across the table. A 38A is built for a 39-inch bust and a 30C for a 33-inch bust. The cup of the 38A holds more than the cup of the 30C. Sizes with the same cup volume run diagonally:
| These hold the same volume |
|---|
| 30C · 32B · 34A |
| 30D · 32C · 34B · 36A |
| 30DD · 32D · 34C · 36B · 38A |
So "I'm a B cup" does not describe a size. A 32B and a 38B are three volumes apart.
Why so many people wear these three letters
A, B and C are the most widely stocked cups, and the most widely worn. Part of the reason is how sizes have traditionally been worked out. Adding four or five inches to the underbust inflates the band and shrinks the cup letter, which places a great many people in a B or C who would measure D or above on a band that fits them.
If you wear a B or C and recognise any of the following, your real size may be a smaller band with a higher letter:
- the band rides up your back,
- the bra is on its tightest hook,
- the centre panel does not touch your chest, or
- there is a slight bulge over the cup after you scoop and swoop.
A 36B with those signs is often a 32D or 32DD. Measure and see.
Fitting an A, B or C well
- Gaping at the top is the most common complaint, especially in moulded cups. It is usually shape and not size. Try an unlined or lower-cut cup before going down a size. See why your bra cups are gaping.
- Wires that feel too wide happen in small cups on larger bands. Plunge styles tend to have narrower wires.
- Non-wired bras and bralettes give plenty of support at these volumes if you prefer them.
- The band still matters. Even with a light bust, a loose band lets the bra shift and ride up.
Above and below
Below A is AA: see the AA cup guide. Above C is D, then DD: see the D cup guide. The complete ladder is in UK cup sizes in order.
Frequently asked questions
What is the difference between an A, B and C cup?
One inch of bust measurement each, on the same band. An A is a one-inch difference between bust and band, a B two inches, and a C three inches.
Is a C cup average?
It is often described that way, but there is no reliable basis for it, and a C on a 30 band is very different from a C on a 40. Many people wearing a C on a loose band measure as a D or DD on a band that fits.
Is a 36B bigger than a 34C?
The cups hold the same volume. The 36B has a longer band. They are sister sizes.
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