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How Do You Measure Up? Our Guide To Bra Sizing


Why is getting underwear sizing right so important?

Sizing is a super important issue for us at ColieCo, and one we take very seriously as we want you all to be wearing lingerie that fits properly.

Not only does correctly fitting underwear make life more comfortable, but it is also more likely to be worn for longer before being retired (and ideally recycled).

Whether you wear bras or bralettes, you may have spent some time entering measurements you have taken yourself into online bra size calculators only to be baffled by each one you try returning a different result. It is a complicated science; different countries use different scales and different companies use different sizing.

You may well have asked yourself, "Should I be measuring in inches or centimetres?", "Why doesn't my underband measurement give my band size?", "Why can't I find a UK bra in a 36DDD?"... There is a long, long list of potential stumpers.

I can't answer every possible quandary in a single blog post; but I can at least explain how we size our bras and bralettes at ColieCo. Hopefully, this will help ensure you get exactly what you need when you order your new ethically-handmade, sustainable lingerie from us!


Scissors and measuring tape


I was educated on pattern grading and sizing in the UK before moving to Portugal and so at ColieCo we use the UK sizing scale. The UK scale is similar to the US scale in that it uses inches rather than centimetres, and gives the underband size (30, 32, 34, etc.) and then the cup size (A, B, C, etc.).

The UK scale only starts to differ from the US scale after you hit a DD cup. This is where the UK scale goes to an E cup, unlike the US scale, which uses a triple D.

Determining band size

I was taught to use the 'plus four' method for determining band size.

To arrive at a band size using the 'plus four' method, we take the measurement for the under bust in inches, round down to the nearest even number, then add four. Using my own measurements as an example, my under bust measures 29", so I round down to the nearest even number (which is 28) and add four, giving an under band size of a 32.

There are different methods, and lingerie designers could argue all day about this one (although I would rather we didn't - let's keep it peaceful 😊), but this is the approach we use. (If you would like to read more about the subject, a good starting point is this post over on the Lingerie Addict's blog.)

Determining cup size

Moving on to cup size, we start by measuring around the fullest part of the bust (normally over the nipple). Taking this figure (again in inches), we subtract the under bust measurement, then, starting at an A cup, we add a cup size for every inch (i.e. A=1, B=2, etc.). Again using myself as an example, my initial measurement is 33". I take this and subtract my under bust measurement (29") which leaves me with 4. Counting from an A cup and adding a cup size for every inch, this leaves me with a D cup. So I am roughly a 32D.

This means that 32D will be the size I start at when I try on any bra, and then depending on the style, how tight the band is and how the cups sit, I might try on my sister sizes. (Sister sizes for any given bra size are found by going up a band size and down a cup size, and by going down a band size and up a cup size. So my sister sizes are 34C and a 30DD.)

At ColieCo, we recognise that when shopping for lingerie online, people don't have the luxury of trying various fits and sizes before deciding what to purchase. This is why we have developed the majority of our bras and bralettes to be size-flexible; for example, adding adjustable back bands allowing you to tweak for a perfect fit.


ColieCo adjustable lingerie design features


Our top tips for accurate measuring

Here are ColieCo's top tips to help you get your measuring right:

  • Stand in front of a mirror so you can see exactly what you are doing
  • Have a pen and paper to hand to jot measurements down as you go, so you don't make mistakes trying to remember several numbers
  • Make sure that the tape measure is parallel to the ground at all times - diagonal lines give inaccurate measurements
  • Wear your best fitting, non padded bra when you measure
  • If you are measuring in centimetres, use Google calculator to quickly and easily convert to inches

Once you know your bra size and sister sizes, take a look at our size chart to discover which size you should order. If you don't see your size in the chart, pop us an email at and we'll help you out with advice on a custom order.

Every single ColieCo garment is ethically handmade to order in the ColieCo Studio, so we're ready to make the adjustments you need to get the perfect fit. It may be that we need to put a smaller or larger back band onto the cups for you. The same goes for our panties and bodysuits; if you happen to have a smaller waist/hip ratio, for example, we can work up custom-sized garments to fit.

As always, we'd love to hear your thoughts!

Find us on social media or drop us a message to continue the conversation!

Nicole x

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