What does ABCD mean in bra size?

ABCD in bra size represents the cup letter, which is the difference in inches between your bust measurement and your band size. A = 1 inch difference, B = 2 inches, C = 3 inches, D = 4 inches, DD/E = 5 inches. It does not represent an absolute breast size.

Is A cup small and D cup large?

Not exactly. Cup letters only indicate the ratio between your bust and band. A 32D holds roughly the same volume as a 34C or 36B. Meanwhile a 40A is a much larger physical cup than a 32D even though the letter is 'smaller.' Always consider both the band number and the cup letter together.

What bra cup size comes after D?

After D, US sizing uses DD, DDD, G, H, I, J, K. UK sizing uses DD, E, F, FF, G, GG, H, HH. A US DDD is the same volume as a UK E. Always check the brand's sizing system when shopping internationally.

Why does the same cup letter look different on different people?

Because the cup letter is relative to the band size. A 34C and a 38C both have a 3-inch cup-to-band difference, but the 38C holds much more physical volume because the entire bra is scaled up. This is also why sister sizes exist — a 34C, 36B, and 32D all hold the same cup volume despite different letters.

What Is ABCD in Bra Size? Cup Letters Explained

If you've ever looked at a bra tag and wondered what the letter actually means, you're not alone. A, B, C, D — they're not random grades. Each letter stands for a specific measurement difference that determines how much space the cup provides.

ABCD Is a Difference, Not a Size

Here's the most important thing to understand: the letter tells you the difference in inches between your band size and your bust measurement. It does not tell you how big your breasts are in absolute terms.

The formula is simple:

Bust Measurement − Band Size = Cup Letter

1 inch difference = A cup
2 inch difference = B cup
3 inch difference = C cup
4 inch difference = D cup
5 inch difference = DD or E cup
6 inch difference = DDD or F cup

Why the Same Letter Looks Different on Different Bands

A 34C and a 38C both have a 3-inch difference, but the 38C holds much more volume because the band (and therefore the entire bra) is scaled up. Think of it as a比例: the cup on a 38C is physically wider and deeper even though the letter is the same.

This is where sister sizes come in. A 34C holds the same volume as a 36B and a 32D. The cup volume shifts as the band changes. So if someone says "I'm a C cup" without mentioning their band size, it doesn't actually tell you much.

Common Misconceptions About ABCD

"A is small, D is huge"

Not exactly. A 32D holds roughly the same volume as a 34C or a 36B — which is a moderate, average size. Meanwhile a 40A is a much larger physical cup than a 32D, even though the letter is "smaller." The band size matters just as much as the letter.

"I need to size up the band to get a bigger cup"

If your band fits correctly, changing the band size to chase a bigger cup letter will give you a poor fit. Instead, increase the cup letter while keeping the same band — e.g., from 34C to 34D.

"The higher the letter, the more rare"

Not at all. DD, E, F, G, and beyond are perfectly common sizes. Most Indian brands now carry up to an H cup. The myth that D+ is "unusual" stops many women from finding their correct size.

Beyond D: What Comes Next?

After D, most brands follow either US or UK sizing:

US sizing: DD, DDD, G, H, I, J, K
UK sizing: DD, E, F, FF, G, GG, H, HH

Yes, this is confusing. A US DDD is the same volume as a UK E. That's why it's important to check the brand's sizing system. Use our Size Converter to translate between countries.

How to Find Your Letter

Measure your band. Wrap a tape snugly under your bust. Round to the nearest even number (that's your band size).
Measure your bust. Wrap the tape around the fullest part of your chest. Don't pull tight.
Subtract. Bust − Band = difference in inches. Match it to the chart above.

For a more detailed walkthrough, see our full guide on how to measure your bra size.

The Bottom Line

ABCD isn't a rating of breast size — it's a measurement of the difference between your bust and your ribcage. The same letter can look completely different on two people with different band sizes. Always pay attention to both numbers, and don't get hung up on the letter alone.