What is my UK cup size? How to calculate the bra cup size…

My articles contain affiliate links. Please see my full disclosure at the bottom of the page.

You might have some idea of what cup size you are. Or you might have no idea at all. Without knowing your band size there’s no telling what your cup size is. Read more

woman wearing bamboo seamless bra

Boody | Organic Bamboo Underwear | Seamless Bra | See Amazon


How do you know your cup size is A, B, C, or D?

Choosing a cup size always starts with determining your bra band size first.


What's your bra size? See my calculator

Marks and Spencer Lingerie

Find the right bra at your M&S Store
M&S UK | M&S US | M&S CA | M&S AU

At Marks and Spencer, you'll find advice and tips on styles to suit you | M&S BraFit Guide


women with measure tap cup size

Let me give you an example.

Remember that bras 75A and 75B have different cup volumes. And bras 75A and 80AA have the same cup volume.

So if you wear 75B but find the band a bit too tight and cups just fine, you should try 80A instead.


Which cup is bigger?

different bras illustrating which cup size is bigger


The bras 90C, 95B and 85D all have the same cup volume.

Really?

Yes, they have. Bras with different numbers can have the same cup volume. It’s called sister sizes.


Marks and Spencer | Women's Fashion 2024

At Marks and Spencer, you'll find advice and tips on styles to suit you | M&S BraFit Guide


What does my example tell you?


Always start by finding the right bra band size

As bras with different band sizes can have the same cup volume, it’s a first to get that band size of yours right.

Another example.

A woman measures her bra size 36C. However, the band may feel too tight or a bit too loose.

If she’s happy about the cup size, she wouldn’t need to change this, wouldn’t she?

In this case, she simply goes up or down a band. But to keep the volume of her cup size, she has to change the cup number as well.

Taking a wider band will automatically change the cup volume as well.

So to keep the same cup volume she would choose:

  • band size down? – up a cup size – 34D
  • band size up? – down a cup size – 38B


Other articles you might like

Guide how to measure your bra size
How often does a bra size change?
The average UK bra cup
Determine your best bra band size
Small bra size chart AAA-B
UK bra size chart
Why is my bra hurting me?
Buying my first bra
6 Strapless bras for girls and teens
How to do the measurements at home


What's your bra size? See my calculator

Marks and Spencer Lingerie

Find the right bra at your M&S Store
M&S UK | M&S US | M&S CA | M&S AU