What Does “Small Cup” Actually Mean? (And Why Most Women Are Mis-Sized)
If you’ve ever been told you’re small-chested but still struggle to find bras that fit properly, you’re not imagining things.
The phrase “small cup” is one of the most misunderstood terms in lingerie - and it’s the reason so many women end up wearing bras that gape, wrinkle, or simply don’t feel right.
Let’s clear it up properly.
What a bra cup size really measures
A bra cup size does not measure breast size on its own.
Cup size is calculated based on the difference between your ribcage measurement and your bust measurement. That means cup size only makes sense in relation to the band size.
In other words:
- A 30A and a 36A are not the same volume
- The letter alone tells you very little
This is where most confusion begins.
Why band size changes everything
Band size is the foundation of bra fit.
When the band is too loose, everything else is compromised.
A too-large band can cause:
- Gaping cups
- Slipping straps
- Lack of support
- Bras that look fine in the mirror but feel wrong all day
Many women who believe they need a “small cup” are actually wearing a band size that’s too big, which throws off the entire fit.
This is especially common for small-busted women.
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Common myths about A and AA and AAA cups
There are a few myths that refuse to disappear:
“AAA cups are tiny”
Not always. An AAAA cup on a smaller band can be very petite, but on a larger band it can represent more volume.
“B cups are average”
There is no universal “average” cup size. Proportion matters far more than letters.
“If you’re small-busted, fit doesn’t matter as much”
This is simply untrue. In fact, fit precision matters more for smaller busts.
Cup letters don’t define your body - proportions do.
Why many small-busted women are wearing the wrong size
If you’ve experienced:
- Bras that gape at the top
- Cups that wrinkle or collapse
- Styles that feel bulky or awkward
- A sense that bras are designed for someone else
- Straps falling down however much you shorten them
…it’s likely a fit and proportion issue, not a body issue.
Many bras are scaled down from larger sizes rather than designed specifically for small cups. This leads to excess fabric, poor shaping, and discomfort - even when the size label looks “right”. At Littlewomen.com we've been making bras designed specifically for the physiology of a small bust customer - longer straps and flatter centre panels that address the common issues faced by small cup customers.
Small bust vs small cup: they’re not always the same
This is an important distinction.
You can:
- Have a small bust but not wear a traditionally “small” cup
- Wear a small cup but not consider yourself flat-chested
- Breast shape, ribcage size, and distribution all play a role. This is why relying on cup letters alone rarely leads to a good fit.
Signs you might be mis-sized
You may be wearing the wrong bra size if:
- Your cups gape or wrinkle
- Your straps constantly slip
- Your band rides up your back
- Your bra disappears under clothes instead of enhancing shape
These issues are common - and they’re fixable.
Why “small cup” deserves better design
Small-busted women don’t need bras that try to add volume or exaggerate shape.
What actually works better is:
- Lighter construction
- Shallower cups
- Thoughtful seaming
- Proportions designed specifically for smaller chests
- Longer straps
When a bra is designed for a small cup - rather than adapted - the difference is immediate. Something we've been promoting (and delivering!) for over 30 years.
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Frequently asked questions
Is an A cup always considered small?
No. Cup size must be viewed alongside band size. An A cup on a small band can be very petite, but on a larger band it represents more volume.
Is a B cup small?
Sometimes. B cups are often described as “average”, but that label is meaningless without band size and shape.
Can you be small-busted but not wear a small cup?
Yes. Many women with small busts need better cup shape, not a smaller letter.
The bottom line
“Small cup” doesn’t mean insignificant, flat, or easy to fit.
It means specific proportions, and those proportions deserve bras that are designed with care, precision, and understanding - not assumptions.
If bras have never quite worked for you, it’s worth questioning the sizing system rather than your body.