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11 Sports Bra Brands and How They Measure Bra Size - The Confusing World of Bra Sizing

Hands up who has a drawer full of sport bras they never wear? Even though you have always been a 36D, yet this pile of 36D’s just don’t fit right? Yep, that used to be me too! But since working in the sports bra industry I have learnt that depending on how the brand measures for their size, I can swing (no pun intended) from a 28 – 32 in the underband and a D – F in the cup. Welcome to the confusing world of bra sizing.

cup and underband measuring

We are tackling this often talked about but not very well understood subject of bra measuring madness, by brand, to help you understand your breasts and size a little bit better.


Let’s start with the cups. It’s kind of bizarre that our boobs are assigned a letter or sometimes multiple letters, right? Before I worked in this industry, I never questioned why, but simply put, letters (B, C, D, DD) = cup sizes. Cup sizes were first introduced in the 1930s and apparel brand; S.H Camp & Company were one of the first to offer alpha sizing (S, M, L) in the underband, in conjunction with A – D cups, we still don't fully understand why letters were chosen. Even more bizarrely, the letters back then were based on how droopy the breasts were, rather than the volume of the breast, which thankfully cup sizes are based on to this day.


The underband size (30, 32, 34, etc) is more straightforward, generally the measurement of where your underband sits (in inches) correlates to the underband size; 34 inches = 34 underband. But not all brands use this method, some may add on 2 or 4 to your underband measurement.

The issue the bra industry has found itself in, is that there is no set standardization for bra sizing, measuring and labelling, therefore each company could potentially have their own standards and methods, which explains why you don’t always fit the size you think you are.

As an example, many European brands don’t use double letter cup sizes. Meaning if you are ‘normally’ a DD in a UK brand, this would convert to an E cup in a European brand. Then American brands introduced DDD cups which convert to our E cup or a European F cup.… stay with me, I promise we make it easier.

All of the above can make it incredibly difficult to be 100% certain of your size. Depending on which country you live in, which brand you buy, the style of bra you wear, or how you or someone else measures you can all result in the outcome of different sizes. Ultimately what it comes down to is a combination of measurements and fit. Size is a great starting point, but at the end of the day it won’t matter what the label says, if it doesn’t fit right, the bra will end up in the drawer with the rest of them, but our aim is to stop that from happening.

How They Measure - Changing from Brand to Brand

We understand how puzzling this can be when trying to work out your MAAREE size from your current bra. So we’ve tried to make this as easy as possible for you; click your current sports bra brand below to check how they measure up and your MAAREE size conversion.

MAAREE / Brooks / Shock Absorber / M&S / Sweaty Betty / Lululemon / Nike / Panache / Runderwear / Anita / adidas

Can’t see a specific brand listed here? Fear not! Drop us an email and we will do our best to help with the size conversion. Or, book a virtual fitting with us so we can get you measured.


Firstly how we measure: At MAAREE, we ask you use a tape measure, pulled snugly around your under bust. This can be in low impact bra, crop top or t-shirt, just not a padded or shaping bra, as this will effect the measures taken. This measure in inches is your underband size. If you measure an odd number e.g. 31 inches you should move up to the nearest even size, in this instance 32.

For your cup measure, place the tape (this part is often squishy so don't pull tight on this one) around the fullest part of your breast, keeping the tape level. The difference between your underband size (32 in this example) and your bust measure (lets say 37 inches) equates to your cup size. A difference of 1 is an A cup, 2 is a B, and so on. In this example, with a difference of 5, you would be a 32DD.

How to find your bra size


You can also use our bra measuring calculator to find your right size. Easy right!




How they measure: Brooks will measure the underband, round up to the nearest even number if odd, and then add on 4 inches. Therefore, if your band measurement is 31 inches you will be a 36 in Brooks bras. It is extremely unclear the method they use for measuring the cup.​ We couldn't even make sense of it! 

Your MAAREE conversion: As we are unsure of the Brooks bra measuring method, we recommend using our measuring guide here.

Shock Absorber

How they measure: Shock Absorber recommends going up a underband size from your regular bra, therefore if you normally wear a 36E, you would be a 38E.​

Your MAAREE conversion: From your Shock Absorber size go down 1 size in the underband only. For example, if you're a 38E in Shock Absorber 38E try a 36E with MAAREE.


How they measure: M&S do not share bra measuring information on their website, however they have been known to add either 2 or 4 inches to your underband measurement (which is the equivalent to 1 or 2 underband sizes), this may come down to who has done the fitting for you and how they have been trained.​

Your MAAREE conversion: As we are unsure of the M&S bra measuring method, we recommend using our measuring guide here. It will however likely be one or two underband sizes smaller.

Sweaty Betty

How they measure: Sweaty Betty measures the same way as us! However, we are aware that some of their sports bras come up very tight.

Your MAAREE conversion: Stick to the same size as your Sweaty Betty bra, unless you know you've already had to size up with them.


How they measure: Lululemon measures (pretty much) the same way as us! Although it's in cm, so can be more difficult to get your head around. It is worth noting that some of their reviews suggest their sports bras come up small.​

Your MAAREE conversion: Stick to the same size as your Lululemon bra.


How they measure: Nike recommends to size up 1-2 underband sizes depending on your measurement. Cups are also measured smaller.​

Your MAAREE conversion: From your Nike bra, if you wear a 36D in a Nike sports bra, try a 34F in a Maaree bra.


How they measure: Panache measures the same way as us! Hooray!​

Your MAAREE conversion: Stick to the same size as your Panache sports bra.


How they measure: Runderwear takes the measurement of your underband in inches, rounded up to the nearest even number, then add on 4 inches. Therefore, if you measure 29 inches you will be a 34 in their underband. Cups are measured in the same method as us.​

Your MAAREE conversion: From your Runderwear size, go down 2 underband sizes. Example: Runderwear 34E / MAAREE 30E.


How they measure: Anita recommends adding 2 inches onto your underband measurement. However, the cup is measured in the same way as us.​

Your MAAREE conversion: From your Anita size, go down 1 underband size and keep the same cup letter. Example: Anita 32C / MAAREE 30C.


How they measure: Not gonna lie, we struggled with this one. One day their calculator was completely broken and then we checked back a few weeks later to find their page had been updated. However, it was still very unclear. Firstly, they don't seem to cater to any cup sizes above DD, secondly they don't provide sports bras that are truly separated out into cup and bust sizes, and thirdly they don't explain to you how to figure out your cup size. You're just meant to already know.

Your MAAREE conversion: The jury's out on this one, I'm afraid. The advice is insufficient. As we are unsure of the adidas bra measuring method, we recommend using our measuring guide here.


There is no wonder so many people are confused about which bra size they need when the measuring advice across all the different sites are this varied. This is why we at MAAREE are keen to teach all women about how to measure for their own bra size, know the signs of an ill-fitting bra and determine how it needs to change from brand to brand. You can be your own bra fitting pro!

We hope the above advice can be a step in the direction to better understand bra sizing. If there's any other aspects or brands you'd like us to cover, let us know in the comments below!

Written by Amber Marchant


Amber - MAAREE Hi, I'm Amber, another Sports Bra and breast health enthusiast. My passion for supporting breasts started in 2016 when I worked for a global sports brand managing their apparel business. I was taught everything I know by the leading Breast Health experts at Portsmouth University and have since been on a mission to educate as many people as possible about breasts. I am originally from the not-so-sunny seaside town of Brighton but have since moved to Mexico to find sunnier spots and sandy beaches. My favourite MAAREE product is the Solidarity High Impact sports bra, have you seen the new Forest Green colour? It's lush!


Farrell-Beck, J, Gau, C. (2002). Uplift: The Bra in America. University of Pennsylvania Press.


Shock Absorber:

Sweaty Betty:






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