What Does 28B Bra Size Mean? A complete Guide on 28b Bra Size!

Unhooked India
Sep 23
7 min read

Updated: Sep 24

Bra sizing can be quite tricky. For many women, and especially those with smaller ribs, sizes such as 28B are not only unfamiliar-sounding but also odd.

What does the “28” actually mean ? Does a B cup have to be the same size? And why does finding it at the store seem nearly impossible? 

If you’ve found yourself in the awkwardness of being between sizes, buying bras that don’t fit quite right, or possibly wondering if “28B” was just “small, you’ve place to be!

This blog will take you through the key terms of 28B, how that is measured in inches and centimeters, what sister sizes you could try, how does 30B compare, and most importantly, how to know if this size fits you.

What Does 28B Bra Size Mean?

Every bra size is made up of two parts: the band size and the cup size.

The Band (28): This is the number in your bra size. It represents the measurement around your ribcage, just under your bust. A 28 band size means your underbust measurement is around 28 inches (or 71 cm). This is considered a petite or narrow ribcage measurement.

The Cup (B): The letter shows the difference between your bust and band measurement. In most bra sizing systems, each cup step equals about 1 inch (2.5 cm). A “B” cup means your bust is around 2 inches larger than your underbust.

So, 28B = 28-inch ribcage with 30-inch bust.

You may also like: What Does B Size Bra Mean?

It’s important to highlight something most people get wrong:

A 28B cup is not the same volume as a 34B cup.
Cup size depends on the band size. The smaller the band, the smaller the actual cup volume.

This is why someone wearing a 34B might look bigger than someone in a 28B — even though both are technically a “B cup.”

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What is 28B Bra Size in CM?

Since many countries (including Europe and Asia) use centimeters, it’s useful to translate.

Band size (28 inches): ~71 cm underbust.
Bust difference for B cup: ~5 cm larger than underbust.
Total bust measurement for 28B: ~76 cm.

Here’s a comparison chart:

Size	Underbust (cm)	Bust (cm)	Difference	Cup Size
28A	~71	~74	3 cm	A cup
28B	~71	~76	5 cm	B cup
28C	~71	~78	7 cm	C cup

This shows how subtle the differences are. Just a 2 cm change in bust measurement can move you from an A to a C. That’s why measuring correctly matters so much.

Is 28B Bra Size Small?

This is probably the most searched question. The quick answer is: Yes, it’s considered on the smaller side, but “small” is relative.

Here’s why:

On a petite body with a narrow ribcage, a 28B can look balanced and even fuller.
On someone taller or broader, a 28B might look much smaller proportionally.

Think about it visually:

Imagine two women — one 5’0” with a tiny frame, another 5’8” with a broad build. Both wear a 28B. On the petite woman, it may look naturally proportional. On the taller woman, it may appear smaller.

It’s also important to separate the social perception of “B cup” from the reality. Because the cup size changes with the band, a 28B cup is actually closer in volume to a 32A than a 34B.

So, if you’ve been told a B cup is “average,” remember: that depends on the band. For petite women, 28B is completely normal.

What Are the Sister Sizes of 28B?

Sister sizes are bras that have the same cup volume but different band sizes.

For 28B, the sister sizes are:

26C → Smaller band, same cup volume.
30A → Larger band, same cup volume.

Try our Free tool for finding the Perfect Sister Size: Bra Sister Size Finder

This is a lifesaver if:

The band feels too tight → Try a 30A.
The band feels too loose → Try a 26C (though 26 bands are very rare).

Example scenario: You are sized as a 28B bra size, but you go to any bra store at the mall and you cannot find a 28 in the store.

The store may actually represent a 30A bra size you can try on. A bra with a 30A cup size is exactly like the 28B cup, but the band is looser and you can probably keep it on the last hook or might have to get an alteration.

Sister sizing is very relative for those less common bra sizes like 28B; it’s just giving you another option and is not sacrificing the fit.

What’s the Difference Between 28B and 30B?

This is where people often get confused. At first glance, both are “B cups,” so they must be the same, right? Not exactly.

Here’s the difference:

Band size: 28 is tighter/snugger; 30 is looser by about 2 inches (5 cm).
Cup size: 30B actually has slightly more cup volume than 28B.

Difference Between 28B Bra size and 30B Bra Size Infographic

So if you switch from 28B to 30B:

The band loosens up.
The cups feel a little bigger.

This is exactly why a 30B is not a true replacement for a 28B. If your band truly measures 28, the 30 may roll up your back and sit less securely.

Quick tip: If you want to stop wearing a 28B but want the same cup volume, go the 30A, not the 30B. Shop: 30B Bras

How Do You Measure for a 28B Bra Size?

Getting your size right starts with measuring. Here’s how:

Measure underbust (band):Wrap the tape snugly under your bust. Round to the nearest whole number. If it’s around 28 inches (71 cm), your band size is 28.
Measure overbust (bust):Measure around the fullest part of your bust, standing naturally.
Calculate the difference:Bust – Band = Cup size.
- 1 inch = A cup
- 2 inches = B cup
- 3 inches = C cup

Example:

Underbust = 28 inches
Bust = 30 inches
Difference = 2 inches = B cupResult = 28B

Mistakes to avoid:

Don’t measure in padded bras.
Don’t round up too much.
Don’t pull the tape too tight.

Can I Find 28B Bras in Regular Stores?

Here’s the reality: 28B is rare in most retail outlets.

Most big-name brands start at 32 band sizes, so if you walk into a mall store, you’ll likely only see 32A and above.

What Styles Work Best for 28B Size?

Some bra styles are better suited for small bands such as 28:

Balconette bras: lift and shape without a lot of padding
Plunge bras: create a nice cleavage effect on a smaller frame
T-shirt bras: padded and seams that work great for every day outfits
Wireless bras: nice for comfort if you do not want underwire
Bralettes: comfy for hanging out but typically not super supportive

Since petite women's straps tend to slide off their shoulder, look for a bra with straps that are closer together or a racerback style.

Does a 28B Look Like “Flat-Chested”?

Not at all — that’s a myth.

Here’s why:

A 28B has less cup volume than a 34B, but on a smaller frame, it can look fuller.
Body proportions matter more than the size label.

For example, on a petite woman with a narrow ribcage, a 28B might look balanced or even slightly curvy. On someone with a broader chest, the same measurement might look smaller.

The “flat-chested” label often comes from comparing cup letters without understanding band size. Once you understand proportionality, it makes sense why a 28B can look very different on different women.

Should I Choose Padded or Non-Padded Bras in 28B?

This depends on personal preference:

Padded bras:
- Add shape and smoothness.
- Great under fitted tops.
- Provide a boost if you want a little extra volume.

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Non-padded bras:
- More natural silhouette.
- Lighter and breathable.
- Comfortable for everyday wear.

Many 28B women find having both options helpful — padded for going out, non-padded for lounging or daily use.

How Do I Know If My 28B Bra Really Fits?

Here are the three checks:

Band fit: Should sit snugly around your ribcage without riding up. You should be able to slip 2 fingers under it.
Cup fit: No gaping at the top, no spillage at the sides. The fabric should sit smoothly.
Strap fit: Should rest comfortably on your shoulders without digging in or sliding off.

If any of these are off, you may need to try a sister size or a different style.

Related Comparisons People Often Search

28A vs 28B vs 28C: Each step adds about 2–2.5 cm in bust measurement. The difference is subtle but noticeable in fit.
28B vs 32A: Similar cup volume, but 32A has a looser band.
28B vs 30A: Identical cup volume, but 30A’s band is larger.
28B for teens: Yes, this is a common size for teenagers or naturally petite women.

These comparisons help women understand why bras don’t always fit the same even if the cup letter matches.

Tips for Shopping 28B Bras Online

Since 28B isn’t widely available, online shopping is often the best option. Here’s how to make it easier:

Check brand size charts carefully — they’re not all the same.
Read reviews — especially from petite customers.
Start with trusted petite-friendly brands.
Look for adjustable bands and straps.
Don’t be afraid to try sister sizes (30A or 26C).

Conclusion

A 28B bra size simply means a petite ribcage with a modest bust. It’s not “too small” or “average” — it’s just a size like any other. The real key is finding what fits you, not what the label says.

If you’re a 28B: