Everything you need to know about bra fittings

From measuring yourself at home to professional bra fitting, here is the ultimate guide

Woman fitting bra

by Lorna White |

You might be surprised to hear that a staggering 82 per cent of women are wearing the wrong bra!

If you've never had your bra fitted before, it's likely you too might be wearing the wrong size. And one fitting in your adult life isn't enough. From puberty, to pregnancy, to hormonal changes and our menstrual cycle, our boobs can vary in size during our lives, so it's a good idea to have your bra fitted a couple of times in your life.

It's understandable why you might feel a little awkward about getting your bra fitted, after all it's not everyday you strip down to your bra in front of a stranger! But trust us when we say the bra fitters are super professional and friendly, and they'll help you feel at ease and comfortable.

If you're considering a bra fitting and want to know what's involved, we answer your questions about bra fittings, from how you get measured, to how to tell if your bra fits properly.

We spoke to Julia Mercer, M&S Bra Fit Expert and Technical Manager, to get her top tips:

What does bra fitting involve?

Getting professionally measured is usually a quick and simple process. You'll be asked to take off any layers so you're just in your current bra or a vest, and the measurer will go around you with a tape measure, and assess how your current bra looks.

She'll then bring you some new bras to try on, adjusting their straps as she goes, until, like Cinderella, you find the right fit!

Why is it important to get professionally measured?

A bra fitting is about getting the best shape of bra for your body shape. Often women think they'll wear a different size in different shapes, but this is wrong.

A bra fitter can help you get fitted correctly, which sometimes means a different size cup to what you are wearing.

A guide to measuring your bra size from home

To start, all you need is a long mirror and a measuring tape. Stand up straight in front of a full-length mirror wearing an unpadded bra.

Step 1: Measure your band and bust size

Use the tape measure to measure around your ribcage, below where your bra fits. This is your band size.

Then measure around your back and the fullest part of your breasts. This is your bust measurement. Next, round both measurements to the nearest whole number.

Step 2: Calculate your cup size

Start by subtracting your band size from your bust size. Every inch difference goes up another cup size. For example, 1 inch means A and 2 inches mean B, 3 is C and so on. This gives you an approximate bra size.

Step 3: Find the perfect fit

The tape measurements will give you an approximate bra size but to tell if a bra fits you properly you will need to see if the bra fits in all the right places.

The band: To make the band sits properly you should sit straight up. You should also be able to get two fingers underneath the cup and not feel too much resistance. If you can easily go under your bra then you need to go for a small size. If it is difficult to get your fingers in, then try the next size up.

The straps: The tighter the strap does not mean more support. The straps should sit comfortably and not pinch or fall off your shoulders.

The centrepiece between the bra cups: The centre bridge should sit flat to your body without any gaping underneath, but also not digging. If it is loose then you should go up a size.

The wires: The wires should follow the natural curve of your breasts. If they come up too high or too far below the bra will not be supportive.

The cups: If the straps, centre bridge and wires fit properly then the cups should be smooth and perfectly moulded to you. If the cups show any wrinkles or sagging it does not fit you properly.

Follow this video for an easy guide to measuring your bra size

What difference does finding the right bra make to your appearance?

A well-fitting bra will help your posture, give you confidence in your outerwear, and even make you look slimmer and discover your waist again.

If you have a special occasion bring your outfit to your bra fit appointment to fit your bra with your outfit.

How often should we be measured?

We recommend you come in for a bra fitting every six to 12 months, as we change our size if we put weight on or lose weight, and with age.

It’s a free service so always worth taking the time to be fitted.

What are the most common misconceptions about bra sizes?

A whopping 82 per cent of ladies we have fitted are in the wrong size. The most common problem that ladies get wrong is the under band (which is normally too large). The second most common mistake is wearing a cup too small.

There are five key checks to the perfect bra fit

1) Underband – should be parallel to the floor and secure enough that only two fingers can fit under the elastic.

2) Centre front – should sit completely flat against the sternum.

3) Side wire – this should be flat against the ribcage and never digging into breast tissue.

4) Cup capacity – breasts should sit fully into the cup without any spillage.

5) Bra straps – these should be adjusted to just fit two fingers on top of each other, which will give the right pressure for your shoulder.


The best way to check if your bra is fitting correctly is lift up your arms, then twist your body - if the bra stays in place then it's the perfect fit.

How to tell if your bra fits or if you're in the wrong size bra

One of the most common problems we see is when your bra is too big at the underband. You often see bras travelling up the back when the band is too big, and this offers no support to your breasts. The most important area of any bra fit is getting the band right first, with only enough space to get two fingers underneath.

If the bra is too small it will be obvious in the cup, where spillage can be seen at the cleavage area, under the arms and across the back. Because the breast is mainly made up of fat (75 per cent) and 25 per cent glandular tissue, the cup area is the first area to see this. Cups should fully encase the breast, sit fully back at the centre front, and no wires digging into breast tissue.

The other key to getting your perfect fit is selecting the correct bra shape to your body shape. There are only four key shapes: plunge, balcony, full cup and strapless. Most girls can wear a full cup or strapless, but if you have a smaller frame and closer cleavage a plunge will always fit you better. If you have wider shoulders and a gap between your breasts a balcony will always fit you better.

What’s the nation’s most common size?

Ladies' sizes have increased over the last 10 years from 34B to 36D – DD.

What will happen during a professional fitting? What should we wear or bring to prepare?

We only need to measure your underband. The rest of the fit is by visually assessing your body shape and where your breast tissue is on your body.

We prefer you to wear a bra as it lifts your breast tissue into the correct place and our bra fitters can give you your size from that assessment.

Do not worry if the bra you are wearing does not fit you, the fitters can see beyond that for you.

What would you say to women feeling self-conscious about coming in?

There are two ways to book a fitting with M&S, either on our bra fit booking tool online, or in store, just ask at the lingerie bra fitting room. If we can, we will fit you straight away. {#h-there-are-two-ways-to-book-a-fitting-with-m-s-either-on-our-bra-fit-booking-tool-online-or-in-store-just-ask-at-the-lingerie-bra-fitting-room-if-we-can-we-will-fit-you-straight-away}

Research has shown that 23 per cent of women would never use fitting service, purely because they may be shy or don’t like other people seeing them without clothes on, which is why we developed the online bra fit calculator on our website for women who do not wish to be fitted in store. Give it a try here.

Do you need a different size when it comes to sports bras?

No, and this is very important that you wear the same size as in an everyday bra. The bra fit will feel different.

Sports bras are worked on compression, to help protect your breast tissue for when you take part in activity. The bra should be comfortable but reduce the breast movement.

Choose the impact level that suits the sport activity. We sell three levels of support: Medium, for yoga or Pilates, High for racquet sports, and Maximum Impact for performance running or horse riding.

What about mastectomy bras, how does the fitting process differ?

The fitting takes longer for post-surgery bras, as the scar tissue needs to be considered and comfort takes on extra importance. Every woman is different and each operation varies.

Take your time and get advice on your personal needs. All of our bra fitters are trained for this very important area.

blue bra

The best shops to buy bras online

These lingerie retailers have a great range of styles and sizes online


On M&S’ website, you can find all ranges of bra sizes from 28AA-46K at an affordable price.

Delivery: Free delivery on orders over £50 and free UK returns via Royal Mail or Hermes.

John Lewis

John Lewis offers bra sizes from 30A-38F. They also offer swimwear, lingerie and sleepwear.

Delivery: Free on orders over £50, otherwise £3.50. They also offer free returns with click and collect.


Figleaves offer bra sizes from 28D-52D. They also offer lingerie, swimwear, nightwear and sports clothing.

Delivery: Free on orders over £50 and free UK returns via Royal Mail, Collect+ or Hermes


On Bravissimo’s website, you can find larger bra sizes from 28D-40L.

Delivery: Free on orders over £75 and free UK postal returns

Curvy Kate

On Curvy Kate’s website, there is a great selection of own-brand lingerie and swimwear with bra sizes ranging from 28D-44K. They also offer a free online bra fitting service.

Delivery: Free on orders over £50 and free UK postal returns

Pour Moi

Pour Moi offers bra sizes from 30A-44J. You can find all types of products from lingerie, swimwear, nightwear, clothing, hosiery and sportswear.

Delivery: Free on orders over £50 and free UK postal returns

Bra fitting tips

Know your body type – finding which bra shape suits you is just as important as getting the size correct.

Be open minded – try new sizes if recommended by your bra fit expert. Getting used to a new size can feel quite strange to begin with, especially if you have been wearing the wrong size over a long period of time.

Have an idea in your head as to what kind of bra you’re after – whether that’s a day-to-day bra, strapless, sports bra or a style for special occasions.

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