Bra fitting- what you need to know

At Avokado, we fit thousands of women every year and it is incredible how much misunderstanding there is around how a bra is supposed to fit. I recently fit a woman who was amazed that the wires at the front of the bra sat flat against her chest- and she had no idea that it was supposed to sit like that because she had never had this before in a bra EVER! It can be quite life changing to go from wearing the incorrect size to finally finding the bra for you, so we have put together a blog post to help you through the science of bra fitting.

To Measure or not To Measure….

Some lingerie stores use tape measures for bra fitting which they use to find your over bust measurement and under bust measurement and then you have to add numbers or subtract numbers or something along those lines! We actually just use bras themselves when doing a bra fitting because seeing how a bra is fitting you incorrectly gives us the information we need to know what size will fit you correctly!

Using bras for fitting also makes sense because different brands can fit differently, and different bra styles will fit different people differently….so you could end up buying 3  bras that fit you perfectly in 3 different sizes. It would have been impossible to extract that kind of information from a tape measure.

Where is it going wrong?

Band Size

Bad band

One of the most crucial elements of a bra’s support comes from the band. If it is not sufficiently firm around your ribcage, then the weight of your boobs pulling DOWN on the shoulder straps at the front will cause the back of the band to ride UP. This will cause your boobs to droop and the shoulder straps to dig into your shoulders, causing that dreaded ‘dent’ in the shoulders.

Band fit

To correct a loose band you need to go down a band size (or 2 or 3 etc) until the band is fitting snugly around your back when hooked on the loosest ‘eyes’. Unless you are pregnant (see post on maternity fitting), there is no need to hook a new bra on any of the ‘eyes’ other than the loosest, as the bra band will only get bigger over time as the fabric starts to stretch and lose its elasticity. Starting on the loosest set of ‘eyes’ allows you to tighten the bra over time giving you much longer wear out of it.

NOTE: when you go down a band size you need to go up a cup size….more on this further down!


Small cup

Your boobs should be completely encased in the cups, with a smooth line where the fabric at the top of the cup meets your bust. If your boobs are bulging at the top or the sides of the cups, it can give you the dreaded ‘4 boob’ look under clothing. Wearing the cup too small is also pretty uncomfortable as the under wire will be digging into your flesh. If this is happening to you, you need to go up a cup size (or 2 or 3 etc) until the cup is fitting correctly. It is a common myth that you need to increase your band size to help the cup fit- if the band size is nice and snug when hooked on the loosest set of ‘eyes’ then you need to keep it as it is! Just take it up in the cup.

Big cup

If on the other hand you find that there is excess room in the cups and you are not filling them out, then you will need to go down in the cup size. Again, if the band is nice and snug when hooked on the loosest set of ‘eyes’ then keep it as it is and just go down in the cup.


Non flat wire

The wires at the bottom of the cups should sit flat against your ribs. If the wires are standing away, it could be a sign that the cup is too small for you as your boobs are pushing the underwire away from your body.  A good tip is to fill the cups with your boobs ensuring no breast tissue slips under the wire, and if there is any ‘spillage’ at the top or size of the cups, go up a size or two. If the cup seems to be fitting correctly but the wires are standing away, it is likely that the bra is too loose in the band and you will need to take it down a band size (or 2 or 3 etc). If you put your arms up in the air and your boobs fall out the bottom of your bra, then there is something wrong for sure!

What is should look like….

Good fit back

A correctly fitting bra should be nice and snug around your body when hooked on the loosest set of ‘eyes’ and in line with your boobs.

Good fit front

The wires should sit nice and flat against your ribs and chest giving your boobs a nice separation. The wires should fully encase your boobs with no breast tissue poking out over the top or sides.

Not all E’s are equal….

Now here is where we get to the bit that causes the most confusion. The letter in your bra size represents a cup volume and this differs in relation to your band size. This is also known as ‘Sister Sizing’. What it means for your bra size is that the volume (letter) changes with the band size (number).

So for example, a 14DD is the equivalent cup volume to a 12E, and a 10F, and an 8FF, and a 6G and also a 16D, 18C, 20B and 22A.

In bra fitting terms, if you are wearing a 10E and find it is good in the cup but too loose in the band, you therefore want to go down a band size and try an 8- but if you stick with an E in the cup, the 8E will be a whole cup size smaller than the 10E. The size that you would need to try would be the 8F.

Put simply: When you go down a band size you need to go up a cup size. 

Or: When you go up a band size you need to go down a cup size.

Sister size chart

In this chart, the colours show the cup sizes which are the same volume but the letters are different for the different band sizes. So to take the red column as an example. if you are a 6 in the band and wear a HH cup- your breast volume is the same as someone who wears a 24C- it is just the size of your bodies that differs and therefore the area that your boobs are spread over.

It can be quite tricky to get your head around and the media doesn’t help with its perception that “Big Boobs = DD’s” because ‘DD’ doesn’t mean anything without a number in front of it….a 24DD is the equivalent to a 6JJ but a 6DD is the equivalent to a 14A.

Clear as mud?!!! Fortunately, all of the bra fitters at Avokado are fully trained and understand all of this so you don’t have to. And if you are unable to visit us in store, we also offer fittings via Skype.

Any questions, please feel free to leave one in the comments below, otherwise give us a call or drop us an email.

Michelle x

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