What Does 30A Bra Size Mean? Complete 30a Bra Size Guide!

Unhooked India
Sep 2
6 min read

Bra sizing can appear complicated at first glance. For example, labels like "30A" or "32B" or "34C." Most people think the letter (A, B, C…) is strictly cup size, and while the letter is based on cup size, the number in an actual bra size describes a combination of band size and cup size.

A 30A is "small" in relation to the band size. A woman with a 30A is not only small breasted, but they also have a proportionately small ribcage.

In this article we will explore exactly what 30A means in inches and centimeters. We will compare 30A to other bra sizes to explore if it is a small size and how small it is, and what bra styles are typically worn by women in a 30A size.

When we finish, you will have a clear, useful conception of the bra size 30A – and perhaps a little more confidence in understanding how bra sizes work!

What Does 30A Bra Size Mean?

The term 30A is a combination of two parts:

30 (the band size): This number represents the measurement around your ribcage, just under your bust. A 30 band is quite small and usually fits someone with a ribcage measurement of about 25–26 inches (63–67 cm).
A (the cup size): This letter refers to the difference between your bust measurement (around the fullest part of your breasts) and your underbust. For an A cup, the difference is about 1 inch (2.5 cm).

So, a 30A bra size means:

Underbust: ~63–67 cm
Overbust: ~65.5–69.5 cm
Cup difference: 2.5 cm

In simpler terms, a 30A bra size is for women with a petite frame (small ribcage) and smaller bust projection.

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30A Bra Size in Centimeters

To make things clearer, here’s how the sizing breaks down in centimeters:

Band size (30): Around 63–67 cm (underbust)
Bust measurement (for A cup): Around 65.5–69.5 cm
Cup depth difference: ~2.5 cm

This means if you measure 66 cm under your bust and about 68.5 cm around the fullest part of your bust, you’re likely a 30A.

Why Centimeters Matter

Most international bra size charts are based on centimeters, which makes conversions easier across regions (UK, US, EU, etc.). For example:

In Europe (EU), 30A is often labeled as 65A.
In France/Spain, it’s labeled 80A.

Knowing the cm range helps if you’re shopping globally or online.

Difference Between 30A and 30B Bra Size

Difference Between 30A Bra Size and 30B Bra Size

One of the most common confusions is the difference between 30A and 30B.

30A: Bust is 2.5 cm larger than underbust
30B: Bust is 5 cm larger than underbust

So, the only difference is in cup volume. Both have the same band (30), but the 30B has slightly fuller cups than 30A.

Quick Visual:

30A: Smaller cup, less projection
30B: Slightly more rounded, extra depth

It’s important to note that while this seems minor, when you are working with very small sizes - like a 30 band, a matter of 2-3 cm can make a difference!

How Do I know if I am a 30A?

So here is how to figure out if your correct size is a 30A:

Step 1: Measure your underbust.

Measure your ribcage snugly just under your bust by wrapping a measuring tape around and pulling it snug.
If you are measuring around 29-30 inches: then you have a band size of 30!

Step 2: Measure your bust.

Measure the fullest parts of the bust by wrapping the tape around your bust.
Subtract your underbust measurement from this number.

Cup calculation:

1 inch difference = A cup
2 inch difference = B cup
3 inch difference = C cup

If your bust is only 1 inch bigger than your band, you’re likely a 30A.

Signs your bra fits correctly:

The band stays snug without riding up.
Straps don’t dig into your shoulders.
Cups sit flat against your bust without gaping or spillage.

How Does 30A Compare to Other Cup Sizes?

This is where many women get confused. The letter A, B, C, etc. doesn’t mean the same thing across all band sizes.

For example:

30A vs 32A: Same cup volume? No. A 32A has slightly more cup volume than a 30A because the band is wider.
30A vs 32AA: Surprisingly, a 32AA can have almost the same cup volume as a 30A, but the band fit is looser.

Cup Volume Comparison:

30A cup < 32A cup
30A cup ≈ 32AA cup
30A cup << 34B cup

This is why it’s crucial to know that cup size is relative to band size.

Sister Sizes of 30A

Not all brands carry 30A, which can make shopping tricky. That’s where sister sizes come in — alternative sizes that give a similar fit.

For 30A, the sister sizes are:

28B (smaller band, larger cup)
32AA (larger band, smaller cup)

If 30A feels too tight around the band, try 32AA. If the cup feels too small, try 28B.

Body Types That Commonly Wear 30A Bra Size

Petite frames: Women with smaller ribcages often fall into 28–30 bands.
Slim athletes/dancers: They may have toned bodies with smaller bust proportions.
Young teens: Many start with 28A, 30A, or similar sizes as their first bra.

It’s important to note that body type is just a general trend — 30A can fit a wide variety of women.

Best Bra Styles for 30A Women

If you wear a 30A, certain styles tend to complement your frame better:

Bralettes: Light and comfortable for smaller busts.
Balconette bras: Add a subtle lift without over-padding.
Push-up bras: Create extra volume for occasions where you want more definition.
Lightly padded bras: Give a smooth silhouette under fitted tops.

Clothing Tips for 30A

Choosing the right outfits can make a big difference in how confident you feel:

Necklines: Square necks, halter tops, and scoop necks enhance a smaller bust beautifully.
Layers: Blazers and jackets fit easily over a 30A frame without bulk.
Fitted styles: Bodycon dresses or slim-fit tops drape naturally without gaping.

Is 30A Bra Size Small?

Yes, 30A is considered a small bra size because:

The band is narrow (fits petite frames).
The A cup means minimal bust projection.

But "small" is relative. A 30A is small compared to sizes like 34C or 36D, but on someone with a petite ribcage, it looks proportional.

Common Misconception:

Some think "A" means "flat" or "no bust." That’s not true. A 30A bra is designed for women who do have breast tissue, just in a smaller volume relative to their frame.

Is 30A the Same in All Brands?

Use Our Free Tool: International Bra Size Converter

Not exactly. Bra sizing varies between countries and even among brands.

US vs. UK sizes: A US 30A and UK 30A are usually the same, but UK brands sometimes fit tighter in the band.
EU sizes: 30A converts to 65A in European sizing.
Asian sizes: Japanese and Korean brands often run smaller, so a 30A may fit closer to 65B there.

Always check the brand’s sizing chart before buying.

What Does 30A Bra Size Mean in India?

In India, bra sizes follow the same system as the UK. A 30A means the same — 30-inch band, A cup. However, availability can be limited since many brands start at 32 band sizes. Petite women often struggle to find 30A in local stores.

Is 30A Smaller Than 32A?

Yes, but only in the band size. A 32A is designed for a larger ribcage (32 inches) but the same cup volume as 30A. That means the actual breast volume of 30A and 32A is almost identical — it’s the band fit that differs.

Is 30A the Smallest Bra Size?

No. While 30A is on the smaller side, there are smaller options:

28A
28AA
30AA

These sizes are less commonly stocked but do exist.

What is 30A bust?

Underbust: approximately 29-30 inches (74-76 cm)
Bust: approximately 30-31 inches (77-79 cm)

This gives a 1 inch (2.5 cm) bust to band difference..

Can a 30A Wear 32A?

Yes, sometimes. Since 32A is a sister size of 30A, it can work if:

The 30 band feels too tight
You prefer a looser fit around your ribcage

But if you want the most accurate fit, stick to 30A.

Do 30A Bras Exist in Every Brand?

No, unfortunately, Many well-known lingerie brands only go down to 32 bra bands, so 30A bras can be trickier to find. There are specialized brands or online shops that have petite sizes. There are always sister sizing options if a 30A is not available.

Conclusion

So, what’s a 30A bra size? It is designed for women who have a petite ribcage (30 inches) and a smaller cup volume (1-inch difference in bust and band). While often referred to as “small,” it is just a proportional size for specific types of bodies.

If you are a 30A, please remember that comfort and fit trump numbers. Also, try bra sister sizes like 28B and 32AA, play around with size since fit can change based on bra style and do not be afraid if some brands do not carry your exact size. The right bra exists, you just need to be informed on what to look for..