What you thought about bra sizes is wrong! - How to choose the correct bra cup size when changing band size

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WERE YOU ALSO MISTAKEN? The size of bra cups depends on the size of the band (also called underband). Without the band size, a cup size means nothing. Most women don't know about this and keep buying bras wondering why seemingly nothing fits them. It's time to demistify and learn aabout this once and for all! =)

There are multiple bra sizing standards. We will mostly discuss US and EU (also know as International).

Take this as an example: The D-cup in US 30D (EU 75D) and US 36D (EU 90D) does not have the same size (volume). A bra in US 36D (EU 90D) can fit a larger bust than a bra in US 30D (EU 75D).

The size designation of a bra cup (B, C, D etc) does not state the volume of the cups. This part about bra sizes is a bit counter-intuitive and misunderstood. This results in many women choosing the wrong bra size. Read on and we'll explain.

A cup in US 30G (EU 65G) has about the same size (volume) as in US 38C (EU 85C). How can this be?

A bra cup size refers to the difference between the measure under the bust (the bra band) and the measure over the bust where the bust is the biggest. A cup size does NOT say how big of a bust that will fit in the bra cup. The cup size refers only to the difference between a band size and a cup size. The cup size is a comparison to the bra band size. It's relative.

Is the bra band size also a comparison? No! The bra band size (US 34, 36, 38 or EU 75, 80, 85 etc) is easier in the sense that it's based on your under bust measurement alone, and is not a comparison to something else.

Okay, so how does this help me? Adjust the bra cup size when changing the band size!

Change the cup size when changing the band size

The most common mistake women make is buying bras with too large bra bands. The support and lift should come mainly from the bra band. The weight of the bust should be carried by the band, not by the shoulder straps. If the bra band is too big, it will not provide proper support. (More about this in our article on how to choose bra band.)

If the cups fit your bust but the bra band size has to be changed, you will also need to change the cup size. For example, if you change from US 36D (EU 80D) to US 34D (EU 75D) then the cup will feel smaller (since a D-cup in 75D is smaller than a D-cup in 80D). Too small cups can be mistaken for the bra band being too small. This is import and worth repeating: You can incorrectly believe that the bra band is too small even though it's the cups that are too small.

"Sister sizes" - A rule of thumb

When you go down a size in bra band then go up a cup size, e.g. from US 36D (EU 80D) to US 34DD (EU 75E). When you go up a size in bra band, go down a cup size, e.g. from US 36D (EU 80D) to US 38C (EU 85C). This rule of thumb is generally referred to as "Sister sizes". Use our table below to ensure that you are making this conversion correctly.

Conversion tables for choosing the correct bra cup size when changing bra band

Click a bra size standard to scroll down to the corresponding table:

• US
• EU / International

US bra size conversion table for bra band size changes

EU bra size conversion table for bra band size changes

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