Whether you have AA cups or smaller or GG cups or bigger, many women wear bras. The pandemic may have gotten us out of the habit – reaching instead of bralettes, sports bras, or freeing the tatas – but when we have to wear them, how do we choose? Is the band size just the measurement around your ribs or is it something else? What does the cup size mean? Why do different countries have different measurements? How do you know if you’re wearing the right-sized bra in the first place? Should it dig in? Should the middle sit between your breasts? Should the band ride up your back? Why are bras so uncomfortable? We’ve got you covered! Here’s our crash course The Mighty Bra 101, so read this before you shop for a bra.

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A short history of the bra

Why do we even wear bras in the first place? You might wonder as you sit at the desk with the underwire poking the centre of your chest – you know that rogue wire that slips through the front? Even as far back as the 14th century, Minoan female athletes are depicted in bra-like or bikini-like garments. So, the sports bra of sorts has been around for a while.

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From the 16th century onwards, wealthier Western women wore that semi-torture device we know and love in bodice-ripping period dramas, aka the corset (i.e. BridgertonOutlanderGone with the Wind, etc).

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Corsets supported the breasts by transferring the weight to the rib cage and they also compressed said rib cage and internal organs too! I guess not breathing is one way to keep your waistline down (no pun intended). 

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By the early 20th century, garments resembling the more contemporary bra had emerged. French designer Herminie Cadolle is credited for inventing a prototype of the first “modern” bra when in 1869 she cut a corset in two and called it “corselet gorge.” But bras still didn’t take off until World War I’s metal shortages forced women to do their bit – in more ways than one.

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Even though corsets were originally made of whale bones, in 1917, the Chairman of the US War Industries Board, Bernard Baruch, asked women to help out with the war effort and stop buying corsets due to a metal shortage. Metal was needed for the war effort. NPR reports that women saved 28,000 pounds of steel, enough to build two battleships.

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As women also entered the workplace to take over factory jobs and other labouring efforts whilst the men were at war, they needed less restrictive clothing for their work.

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In November 1914, American socialite Marry “Polly” Phelps Jacob patented the “brassiere” (using the pseudonym Caresse Crosby). She’d come up with the concept whilst dressing for a ball. Her corset poked through her dress and she wanted underclothes that didn’t show through. She asked her maid to sew two handkerchiefs together to offer more support and comfort.

image of an early bra drawing

Even though women did start to ditch their corsets for good after and during the war years, large-scale production of bras commercially didn’t occur until the 1930s. Some historians credit the founders of Maidenform, William and Ida Rosenthal with introducing the A, B, C, and D cup system in the late 1920s or early 1930s, yet others claim it was S.H. Camp and Co. who came up with the system. But no matter who came up with it, that system has stuck. Adjustable bands with multiple eye and hook positions also came about in the 30s. So, we use band and cup sizes to measure women’s breast size – and that practice is nearly 100 years old already! You’d think we’d have a better system by now.

image of Patti Page in 1955 wearing a bullet bra

In the western world today, nearly 95% of us women have the (mis)fortune to wear bras, which for manufacturers means a billion-pound industry dominated by companies like Victoria’s Secret. Plus, there are more bra styles now than ever to cater for minimal bras, strapless bras, plunging necklines, backless garments, increasing bust sizes, and more. In the last decade alone, our busts have gotten bustier – with British women jumping from a modest 34B to a heftier 36C.

And even further evolved from the bra, we see everything from boob tape to backless bras to sticky bras and everything in between. But this blog is not about those. We’re here to discuss how to tackle the good, old-fashioned bra.

How do I know if my bra size is wrong?

How do I know if my bra size is wrong?

Let’s face it – we have all worn the wrong size bra at some point in time. Some staggering statistics claim that 80% of women wear the wrong size bra. And the wrong sized bra is uncomfortable.

If you’ve ever had any of the following with your bra, you’re wearing the wrong size and/or you need a new bra size.

  1. The back band rides up your back and doesn’t sit at your ribs.
  2. The cups gape.
  3. Your breasts bulge over the top of your bra.
  4. The centre of the bra doesn’t sit on your breastbone.
  5. The straps dig in your shoulders painfully.
  6. You own a dozen bras yet swap between two or three because those bras are your “go-to” comfy ones (i.e. a few of your bras may be the wrong size).
Your band is riding up your back and doesn’t sit at your ribs

#1 Your band is riding up your back and doesn’t sit at your ribs

If the back of the band is riding up, it means you’re wearing a band size that’s too big for you. The back band will rise if the weight of your breasts a the front pulls the straps down and, therefore, lifts the back band up – making an upside-down u-shape on your back. Since 80% of your bust support should come from your back band, if you don’t have a snug fit, you’re losing vital lift (and comfort). 

The cups gape

#2 The cups gape

If your cups are gaping and your breast tissue is spilling over the top, the cup you’re wearing is too small or too large. The bra cup should encase all of your breast tissue with no space left over. If your breasts aren’t filling the cup, the cup size is too large. 

Your breasts bulge over the top of your bra

#3 Your breasts bulge over the top of your bra

If your breasts are spilling over, similarly, the cup size is too small. Sorry to point out the obvious, but with bra fittings, you determine your band first and then your cup. Cup size is relative to your back size and then you find the cup that will encase your breasts properly, giving you a smooth, lifted appearance.

The centre of the bra doesn’t sit on your breastbone

#4 The centre of the bra doesn’t sit on your breastbone

If the wire isn’t sitting close to your body, you’re wearing the wrong sized bra. On a correctly fitting bra, the underwire should sit against your body firm at each point (even between your breasts). The wires should also sit far enough back under your arms that the wires aren’t pinching any breast tissue. Again, if your back band is out, the wires can move around which allows your breasts to escape from the bottom. The back band should sit firmly so that the wires can also sit against your body – encasing all of your breast tissue and giving you support.

The straps dig in your shoulders painfully

#5 The straps dig in your shoulders painfully

Even though the bra straps do not (as the misconception goes) provide support for your breasts, they are designed to help the rest of the bra do its job. If your bra straps are falling down over your shoulders or digging in, something is wrong. The tension in your bra should be at “two fingers” only, where you can fit two fingers under the strap comfortably. You should adjust your bra straps accordingly. But if your straps are digging in painfully, then they are either too tight or the rest of your bra doesn’t fit correctly and too much weight and the job of support is being placed on your straps. On a side note, you don’t have to shorten and adjust your bra straps to the same length on each side. They just need to ensure the cups fit correctly on each side and sometimes that means they’ll be adjusted to different lengths. 

You own a dozen bras yet swap between two or three because those bras are your “go-to” comfy ones

#6 You own a dozen bras yet swap between two or three because those bras are your “go-to” comfy ones

If you find that only a few of your bras are comfortable (or maybe at worst, one), then that may indicate you’re wearing the wrong size. Try on each bra with the steps above in mind. You may (very unfortunately since bras are expensive) need to shop again. But your body will thank you when you find the right fit!

So, you have all that information, but what now? You may have determined that your bra falls into one or more of the categories above. How do you ensure you have the right fit? Well, the components of a bra are the band, cups, straps, and centre gore. Let’s find out how to find your size.

How do I measure for the correct size bra?

How do I measure for the correct size bra?

A good bra goes unnoticed but a bad one gives bras a bad name! If you find yourself picking the bra out of your sides or needing to unleash your breasts at the end of the day, you might have the wrong fit, so here’s how to have the right one. Keep in mind that multiple factors do affect the bra you’ll need such as your outfit, the time of the month, and just natural bodily flows as our breasts develop and change over time.

How to measure your band size

How to measure your band size

Without a bra on, measure around your back and under your bust with a tape measure – where the band of your bra would normally sit. Ensure the tape goes around your body in a steady, even line. The measurement should feel snug but not tight. Find your measurement in inches. If your measurement is an even number (i.e. 28, 30, 32, 34, 36, 38, 40, 42, etc), then you’ve already found your band size. If your band size is an odd number, then round up to the nearest inch (i.e. if you’re 29 inches round up to 30 inches, etc).

How to measure your cup size

How to measure your cup size

To measure cup size, pop on your current favourite bra (i.e. the go-to one that’s most comfortable) so that your tatas are held in place where you’d like them to be. Next, measure the fullest part of your chest. 

Take that measurement and subtract your band size from your bust measurement. The difference in inches denotes your cup size. The following measurements are for UK bra sizes only. Other countries use different measurements (yes, it’s totally confusing).

  • 0=AA
  • 1=A
  • 2=B
  • 3=C
  • 4=D
  • 5=DD
  • 6=F
  • 7=FF
  • 8=G
  • 9=GG
  • 10=H
  • 11=HH
  • 12=J
  • 13=JJ
  • 14=K

You will combine your band and cup size so you have a number followed by a letter. For example, if your band is size 30 and your bust is 5 inches bigger than your band size (i.e. you measure 35 inches around the bust) then your bra size is 30DD. 

Once you have your bra-size benchmark, you’ll still need to try on different bras with different styles and fabrics to find one that truly fits well for you. When you’ve adjusted your bra properly, it shouldn’t feel like you’re wearing a bra. 

How to try on bras for the right fit

How to try on bras for the right fit

Once you know your size, grab a few bras to try on. You should always fasten the bra on the last hook. Adjust the straps so they are tight but you can slip two fingers under the strap at your shoulders. When looking sideways in a mirror, your breasts should sit halfway between your shoulders and elbows and when you place a slinky t-shirt over the top, you shouldn’t see any bulging. 

How to try on bras for the right fit

The underwire should track your breasts and follow the line and the cups should encase all of your breast tissue, even under your armpits. If there’s space between the wire and the bottom of your breasts, the cup doesn’t fit quite right and if your underarm breast tissue spills out, then that’s not right either. Your bra strap should sit horizontally around your body and be firm. You should be able to fit three fingers under the band at the back but only two the rest of the way around. The centre gore should be against your breastbone. There are styles with plunging necklines where this centre bit is smaller. 

How to try on bras for the right fit

It sounds confusing and that’s why bra size is so difficult. Even if you have your exact measurement perfectly, bra fitting isn’t an exact science sadly. Your bra size will vary from style to style. Sometimes you’ll have to go up a cup size and down a band size or vice versa. And bras have “sister sizes” where the cups have the same capacity but the band is different sizes. As an example, someone who wears a 32C might wear a 30D and a 34B, depending on if the style of bra they are trying on provides a looser or snugger fit. As a rule, if you go up a cup size, you’ll need to go down a band size. If you go up a band size, you’ll need to go down a cup size. But keep in mind that you need to ensure that the band fits snugly, your breast tissue fits in the cups, the wire is against your ribs, and the straps are holding things in place but not supporting your breasts.

This writer explains all about her journey with trying bras on at different retailers.

Key points about the right fit

Key points about the right fit

Back band

  • Parallel to the floor
  • Fits around your back without any riding up
  • Fit two fingers under the band
  • Snug and doesn’t move
  • Fastened on the loosest setting (last hook)
  • Note: you’ll tighten the bra hooks as your bra stretches to maintain support


  • Fully encase all breast tissue
  • Provides a lifted and smooth appearance
  • No gaping or bulging


  • Sit flat between your breasts
  • Touch your ribcage from the centre of your body to under your arm
  • No digging
  • No excessive movement


  • Sit at two-finger tension on your shoulders
  • No digging in
  • No falling down

The takeaways

Maybe the Victorians had it right and the corset was easier to wear! Jokes aside, if you’re wearing the wrong sized bra, you can measure yourself and go to a bra shop to try on different sized bras, ensuring the bra fits properly because you cannot guarantee even the same sized bra from different brands and makers will fit perfectly. It’s recommended that in addition to your own measuring, you get professionally measured. 

Many UK-based retailers are happy to measure you correctly (often for free) such as M&S, Bravissimo, Boux Avenue, Victoria’s Secret (but beware they’ll sometimes try and fit you into their sizes and their sizing runs small and for smaller-busted ladies), John Lewis, Harvey Nichols, House of Fraser, Fenwick, and speciality lingerie shops. These bra-sizing experts can help you get the best fit and the best look for your body so you can feel confident and cool all day long. Plus, once you have the right fitting bra, you’ll never go back.

Let us know on Tria Beauty UK’s social media where you like to shop for bras.

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