Bra fitting guide

When draping a pattern, I use several detailed measurements of the bust, underbust, overbust etc, but I also ask for your bra size to help me to get the bust area the right size and shape. I have in the past received orders from customers with some very strange measurements – the bra size they gave me simply did not add up. This can make things more difficult, so I have written this bra fitting guide so you can make sure the size you tell me is the right one. Plus the fact that I think everyone should know how bra sizing works!

As many as 95% of women wear the wrong size bra, mainly down to a lack of understanding about how bra sizing works, and how bras are meant to fit. Many bra size guides and even professional fitters will give you a band size which is far too big, often because they are using outdated sizing methods which involved measuring the underbust and adding several inches to get the bra size. (Just like dress sizes, bra sizing has changed over the years.) To give you a rough idea, a band size of 32 should fit an underbust of around 31-32 inches, although how tight it feels will vary from person to person and different brands will often fit differently. The correct band size should be the smallest you can comfortably wear, which means that two people with the same measurements will not necessarily be the same size. Cup sizes are relative and are based on band size.

Using the “traditional” method for calculating bra size in a modern bra results in the band being far too big, and the cups too small – don’t be reluctant to try on a smaller band size and/or larger cup size. Many people feel intimidated by what are considered larger cup sizes, but once you have tried your true size you will see the difference! It is a common misconception that a woman with D or DD cups is extremely well endowed. In fact, a DD cup is about average. If this surprises you, you’re probably wearing the wrong size!

The sizes within the black outline are regarded as being the average range, and are the easiest to find on the high street. The blue section is often classed as large or plus sized, and the sizes in the pink box are considered to be small sizes, i.e. starter/first bras. As the table shows, a huge section of women are not represented by any of these three departments, and consequently most people do not realise that there is a far wider range of sizes in existence, than are made available by retailers. Band sizes go from 28 up to at least 56, and cup sizes start at AA and go up to K. Many people who have not been fitted base their estimate of their own size on what is considered to be average, often leading to wearing a band size which is far too big, and a cup size which is too small. The shaded area represents a more realistic estimate of the range of most common sizes.

Some oft-repeated bra myths:

  • The average bra size in the UK is a 36C.” More bras are sold in 36C than any other size, but this does not make it the true average size by any means. Given that as many as 95% of women are wearing the wrong size bra, a survey of the bras we wear is almost useless in determining the average. Research by Bravissimo found that 60% of C cup wearers should be at least a D cup, and more than half of us are wearing a back size which is too big. The true average size is estimated to be around 34DD.
  • Most women are around a B-C cup. DD cups = huge. FF cups = fake.” In fact, many women are a much bigger cup size than they think because wearing the wrong back size skews the cup size. The average size is around a DD, and a woman can easily be an E or even F cup without looking much bigger than average. People often forget, or are unaware, that cup size is relative – for example, a 28F would be roughly equal to a 36C in volume, and four cup sizes smaller than a 36F.
  • A 32 is small, a 38 is big.” It’s not as simple as that; the band size is only the size of the ribcage and bears no relation to the size of the breasts or the woman’s body shape. Someone with a 32″ band is just as likely to have DD cups (or even E, F, FF etc) as someone who wears a 38. This misconception may be due to the fact that many people incorrectly assume the number in the bra size is the bust measurement.
  • A pair of D-cup breasts weighs around 15 to 23 pounds.” Anyone who understands how bra sizes work will see how ludicrous this claim is. Cup size alone is meaningless without the band size, so this does not give any indication of volume per se. In any case, this statistic gives a very distorted image of how big D cups are. In order to weigh this much, the band size would have to be very large indeed! One source [link] claims that a typical 36C breast (equivalent to a 34D) weighs 0.9kg which equates to just under a pound each – a much more realistic estimate!
  • No-one with a small band size has big boobs unless they’re fake.” As mentioned above, there is no reason why someone with a small band size cannot have a large cup size. People’s idea of what constitutes a “normal” size often comes from the sizes available in the bra shops, so it is understandable that many people equate small band sizes with a flat chest, and large cup sizes with a fuller figure because it’s often only the pre-teen bras which go smaller than a 32 band size, and only the plus size bras which go bigger than a DD cup.
  • The number of the bra size is the bust measurement.” Another myth arising from the confusion of bra sizing. The number in the bra size is the band or back size, and refers to the size of your ribcage, not your bust. If your breasts grow, you need to go up a cup size, not a band size. You only need to get a bigger band size if the one you are wearing is too tight to fasten.
  • A band size 32 is the smallest you can get, so it must be around a size 8.” Many people don’t realise that band sizes actually start from 28, even in larger cup sizes. A band size of 32 is usually closer to a size 12, and if a woman has a large cup size, she could be wearing a size 14-16 and still need a 32″ bra.
  • The bra should fasten on the smallest adjustment to allow you room to grow.” There is little point in allowing room for growth, as your cup size is far more likely to change with weight gain than your band size. Bras will stretch with wear, so if it already fits you on the smallest adjustment, it will quickly become too big. The purpose of the adjustable back is to allow for this stretching.
  • To get your bra size, you have to add 4 to 5 inches to your underbust measurement, then work out your cup size based on your bust measurement. This is an accurate way of determining your size.” Adding this much to your underbust measurement would mean your bra would ride up your back and offer hardly any support, especially if your breasts are heavy. If you are trying to get an idea of your bra size from your measurements, then you should just round your underbust measurement to the nearest even number. Quite apart from that, no formula will work for everyone so the right size is the one that fits!
  • Women with an underbust of less than 33 inches should add 4 or 5 inches to their measurement, and those with an underbust of 33 inches or more should add two to three inches.” This is little more than a ploy to sell a narrow range of sizes to a wide range of consumers. It is possible to convince someone who needs a 28 band size that they will manage with a 32, but of course it would be impossible to fit someone who needs a 38 into a 34, thus the standard size range of 32-38 (just four different sizes!) is marketed to all. There is also an association between large band sizes and large cup sizes, so they are perceived as needing more support and thus a tighter band.
  • The shoulder straps support the breasts.” Most of the weight of the breasts should be supported by the band around the chest, not the shoulder straps. The bra relies on the tension of this band to support the cups, and this is why it’s so important that you wear the correct back size.
  • The size that the lady in the shop tells you is always the right one.” While it is always a good idea to get fitted, it is also important to bear in mind that some fitters are better than others. A 2004 report by consumer watchdog Which? found that almost 80% of bra fittings resulted in a poor fit. Don’t always take the fitter’s word for it – try on a range of sizes to see for yourself and compare with the pointers in this guide. Many shops only stock the “average” sizes, so if you are quite slim and/or a large cup size, they may well put you in the smallest band size and largest cup size they have despite it still not fitting. For example, if you should be a 28F, they might put you in a 32DD. It is advisable to go to a shop which stocks a wide range of sizes. Bravissimo and Rigby & Peller are highly recommended for bra fitting.
  • If the shoulder straps dig in and your back hurts, it means you have very heavy breasts and there’s not much you can do about it short of getting a breast reduction.” If you are suffering pain because of a heavy bust, it’s probably your bra, not you, that needs to change! NHS studies have found that as much as 100% of patients requesting breast reduction were wearing ill-fitting bras. [link] A better fitting bra will support from the chest and not dig into the shoulders as much, so there may not be any need to resort to surgery.
  • A certain amount of spillage is ok – that’s what push-up bras are meant to look like anyway.” Any amount of spillage in any type of bra means the cup size is too small. Even if you have cleavage, there should still be a smooth line at the edge with no “double boob” effect.
  • If your bra leaves red marks around your chest, it means the band size is too small.” The truth is that any bra will leave some marks, even if it’s quite comfortable. If the band is so loose that it leaves no mark on your skin at all, it’s probably too big. Think about how many other types of clothing leave red marks and indentations on you – knicker elastic, the seams of your jeans, waistbands etc but nobody ever says that means they’re too small!
  • The band is meant to be “comfy” and not too tight.” The band of your bra is actually meant to be quite tight. Not so tight that it is painful, of course, but tight enough that it won’t move around much.
  • If the back and sides of your bra make your flesh bulge, it’s too tight.” Bulges around the band of your bra are not necessarily a sign that you need a bigger band size. Wearing a smaller band size can actually reduce bulging, as it will be positioned lower on your back.

Signs that you’re wearing the wrong band size:

The band slides about and rides up at the back. The band of the bra should be horizontal all the way round and quite a snug fit. If you pull the shoulder straps upwards, the band should grip your back. If it slides up easily, or if your boobs pop out under the bottom of the bra, the band is probably two or more sizes too big.

You’re always having to pull the back of the bra down. This could be a sign that it is riding up and you need a tighter band.

The band feels roomy and you can easily fasten the hooks on the smallest adjustment, even when brand new. The band of your bra needs to be a snug fit in order to support the cups, and it should fit on the biggest adjustment so that you are able to tighten it when the elastic starts to wear out. If it fits firmly against your body, but you have to fasten it on the tightest adjustment straight away, it’s probably one size too big (see the centre image below.)

You can stretch the back of your bra away from your body by several inches. You should be able to run a couple of fingers around inside the band to make sure it is not cutting in, but if you can fit more than a fist under the back, it’s too loose.

The shoulder straps dig in. This often means the band is too loose, forcing the straps to take the weight.

The shoulder straps are constantly slipping off. This can be a sign that the band is too big, and therefore designed to fit a larger frame with broader shoulders. The shoulder straps on a smaller band size will be positioned closer together. If you find that you have to loosen the straps to prevent them from cutting in, this is also due to the band being too large and not supportive enough.

Signs that you’re wearing the wrong cup size:

The top edge of the cups make a double bulge. The cups should make a smooth profile, even in push-up styles. If you are spilling out, even a small amount, try a bigger cup size.

The underwires do not lie flat against your sternum in the middle. This is another sign that the cup size is too small, as the breasts are not being contained within the cups and are forcing the centre of the underwires out from your chest (a look often sported by page 3 girls.) If you want to enhance your cleavage, look for a bra designed for this purpose in the right size.

The underwires sit on or poke into breast tissue at any point. This means they are not fully enclosing the breasts. Don’t forget to check the sides of the underwires under your arms, they should lie flat against your ribs in the same way that the centre lies flat against the sternum, with no bulging or spilling out.

The fabric of the cups is wrinkled and loose or there is a large gap at the top. This means you’re not filling them out fully, so you should try a smaller cup size.

So how do I find my true bra size?

Well, firstly, nobody has one true bra size. Bras will vary in size and fit depending on the brand and even the style, so it is far better to familiarise yourself with how a well-fitting bra looks and feels, than to rely on your measurements. I will show you two methods for determining your bra size. Method one will quickly estimate your size based on your current bra size and your underbust measurement, and method two will go into more detail about the fit of your bra.

Method One

This method does require a tape measure, but only to determine the band size. You’ll also need to put on your favourite bra. It helps to stand in front of a mirror to see what you’re doing and to check that the tape measure is horizontal.

The underbust measurement should be taken by holding the tape measure horizontally underneath the breasts. Pull the tape measure firmly against your body so that it feels tight, and don’t breathe in deeply. Don’t worry about it feeling too restrictive – the elasticity of the bra should take care of comfort. You will need to round your underbust measurement to the nearest even number. This usually means rounding up, but if you are closer to the smaller size, you may get a better fit by rounding down. For example, a measurement of 35 inches would usually be rounded up to 36, whereas a measurement of 34.5 inches may be rounded down to 34. The only way to find out which fits better would be to try on both sizes.

Now find your current bra size on the table, and trace along to the correct column for your underbust measurement. You will notice that for each column you move to the left, the band size decreases by two inches and the cup size increases by one letter, and the reverse happens if you move to the right. This is because all the sizes on each row of the table are equivalent in volume. If you were to stay in the same cup size but move to a smaller band size, then the cups would also be smaller. A D cup on a 36″ band is equivalent to a DD cup on a 34″ band, or an E cup on a 32″ band etc.

28A 30AA
28B 30A 32AA
28C 30B 32A 34AA
28D 30C 32B 34A 36AA
28DD 30D 32C 34B 36A 38AA
28E 30DD 32D 34C 36B 38A 40AA
28F 30E 32DD 34D 36C 38B 40A 42AA
28FF 30F 32E 34DD 36D 38C 40B 42A 44AA
28G 30FF 32F 34E 36DD 38D 40C 42B 44A 46AA
28GG 30G 32FF 34F 36E 38DD 40D 42C 44B 46A
28H 30GG 32G 34FF 36F 38E 40DD 42D 44C 46B
28HH 30H 32GG 34G 36FF 38F 40E 42DD 44D 46C
28J 30HH 32H 34GG 36G 38FF 40F 42E 44DD 46D
28JJ 30J 32HH 34H 36GG 38G 40FF 42F 44E 46DD
28K 30JJ 32J 34HH 36H 38GG 40G 42FF 44F 46E
30K 32JJ 34J 36HH 38H 40GG 42G 44FF 46F
32K 34JJ 36J 38HH 40H 42GG 44G 46FF
34K 36JJ 38J 40HH 42H 44GG 46G
36K 38JJ 40J 42HH 44H 46GG
38K 40JJ 42J 44HH 46H
40K 42JJ 44J 46HH
42K 44JJ 46J
44K 46JJ

You should now have an idea of your correct bra size. However, you will still need to try on some bras in your new size to be sure. Once the band is a good fit, you may find that you need to move to a different cup size, which is simply a case of going up or down a letter. If you need to try a different band size, don’t forget that you need to increase the cup by one size for every band size you go down, and vice versa.

Method Two

This simple test does not require a tape measure, and should help you to determine if the bra you are currently wearing fits properly, and if not, what you need to change.

Band Size:

  1. There are usually 3 sets of eyes on which to fasten the hooks of the bra. Start by fastening your bra on the loosest setting and run two fingers around under the edge of the band. How does it feel?
    • a) Very tight. the edges of the band cut in painfully.
    • b) Snug. The bra does not move when I twist around, but it doesn’t cut in either.
    • c) Comfortable, roomy, not very tight.
    • d) Loose. The elastic is hardly under any tension.
  2. With the bra still on the loosest adjustment, take hold of the front of the bra by the band, and pull it outwards from your chest.
    • a) I can barely get my fingers under the band.
    • b) I can only pull it out by an inch or so.
    • c) I can pull it out by a couple of inches or more.
    • d) I can stretch the bra out from my chest by several inches.
  3. Now take hold of the back of the bra, and pull it away from your body. Try to fit the width of your fist under the band. (Refer to the image on the first page.)
    • a) I can only pull it away from my back by an inch or so.
    • b) I can just fit a fist under the band, but no more.
    • c) I can pull it out by four to six inches.
    • d) I can stretch the bra away from my back by more than six inches.
  4. Stand side-on next to a mirror so you can see your back. With the bra still fastened on the largest adjustment, raise your arms and take a look at the band. Is it horizontal all the way around, or is it higher at the back?
    • a) The band is horizontal all the way around or slightly lower at the back, and it grips my body uncomfortably when I move.
    • b) The band is horizontal all the way around or slightly lower at the back, but doesn’t dig in.
    • c) The back of the bra rises up slightly in the middle forming an arch, and it’s a bit higher than the front.
    • d) The back of the bra forms a distinct arch and is noticably higher than the front. It may feel as though your breasts are going to fall out under the band.
  5. Now fasten your bra on the tightest set of eyes. How does it feel now?
    • a) I can’t fasten it on the tightest setting.
    • b) Very tight. Too tight to be comfortable.
    • c) A more snug fit.
    • d) No noticable difference.


  • Mostly a: The band of your bra is probably too small. Try one size larger.
  • Mostly b: It looks like you’re wearing the correct band size.
  • Mostly c: Your band size is too big. Try one size smaller.
  • Mostly d: Your band size is too big. Try two or more sizes smaller.

Cup Size

  1. 1: Look at the top edge of the cups. Do they make a smooth profile, or are you bulging out?
    • a) There is a gap between the fabric and my breast.
    • b) There is a smooth transision between fabric and skin, with no bulge.
    • c) The edges of the cups cut into my breast, making a “double boob,” especially when I breathe in.
  2. 2: Look at the centre gore of the bra, where the cups meet. Does it lie flat against your chest in between your breasts?
    • a) The centre of the bra lies flat against my chest, and the ends of the underwires dig into my breastbone.
    • b) The centre of the bra lies flat against my chest and separates the cups comfortably.
    • c) The underwires are pushed out from my chest by my breasts and do not separate the cups.
  3. 3: Looking at the fabric of the cups, are they filled out properly?
    • a) My breasts don’t seem to fill out the cups as fully as they could, and the fabric is wrinkled all over.
    • b) The fabric is smooth all over, and the cups look and feel filled out.
    • c) The fabric looks very tight, and my breasts feel squashed into the bra.
  4. 4: Standing side-on to a mirror, lift up your arms and look at the sides of the cups. Trace along the underwire with your fingers.
    • a) The cups feel very wide, and the underwires are an inch or more back from the edge of my breast.
    • b) The underwires surround and fully enclose the breasts, with no digging in or bulging out.
    • c) The underwires dig into the sides of my breasts, and the breast tissue spills out into my armpits.


  • Mostly a: The cups are probably too big. Try a smaller cup size.
  • Mostly b: The cup size seems to be correct.
  • Mostly c: The cups are too small. Try one or more cup sizes bigger.

Now that you have identified the fitting problems of your bra, the next step is to combine the band and cup size to see what your new bra size should be. This can seem complicated, but it will become simple once you know how. If the band size is correct, and you only need to change the cup size, then it is simply a case of going up or down a letter. However, if like most women you are wearing the wrong band size, you will also need to change the cup size letter, even if you are not actually changing the cup size. This is because when you go down by one band size, the cups will also be one size smaller. For example, a 34C will be one cup size smaller than a 36C. If, therefore, you are currently wearing a 36C bra and you need a smaller band, you will need to go up by one cup size letter for every band that you go down, in order for the cups to remain the same size, so you will need to try 34D, 32DD etc. You may find it useful to refer to the table from method one.

Getting professionally fitted

If you decide to get a professional bra fitting, it’s important that the fitter examines the way the bra actually fits, rather than simply using a tape measure. If you are measured and told your size straight away, then try somewhere else. The best fitters do not use a tape measure at all.

Fitting tips:

  • When getting fitted for a bra, always go to a shop which stocks the full range of sizes. If you are smaller than a size 12, or if you have a larger than average bust for your size, bear in mind that you might need a size which is unavailable in most shops, and the shop assistant may give you a bra in the wrong size in order to make a sale (or they may not be aware that a better fitting bra exists.)
  • Most people’s breasts fluctuate in size, and they can sometimes grow for no apparent reason, so it’s a good idea to review your size every six months or so.
  • The correct band size is the smallest you can comfortably fasten around your back, and the right cup size is the biggest you can completely fill out with no wrinkles in the fabric.
  • It’s easier than you might think to wear the wrong cup size and not notice, and it’s often only when you try on a bigger size that you realise the old size was too small. It’s always a good idea to try on different cup sizes so you can actually compare.
  • When trying on a new size, avoid heavily padded pushup bras if possible. It can be difficult to tell if they are meant to bulge out or if it’s too small!
  • A new bra should fit on the biggest adjustment to allow for the stretching that will occur as the bra starts to wear out. If it already fits comfortably on the smallest adjustment, go down a band size (and up a cup size to compensate.)
  • If you have uneven cup sizes, go with the bigger side. You can help to support the smaller side by making that strap a bit shorter. If there is a difference of a whole cup size or more, you will probably need to pad out the smaller side with a cookie or chicken fillet. These are available at most lingerie shops.
  • You may find it’s better to buy a new bra when on your period or just before, you’re often slightly bigger then. If your cup size changes a lot, don’t try to squeeze into a bra that’s too small – you may need to have different bras for these days.
  • Always try on a bra before you buy, even if you think you know your size or you’ve bought that brand before.
  • In a correctly fitting, supportive bra, your bustline will normally be around half way between your shoulder and your elbow, although your bust may be naturally positioned lower or higher on your chest.
  • Don’t forget to adjust the shoulder straps. They should be tight enough to stay on your shoulders, but they shouldn’t dig in.
  • If you find the bra lacks support unless you make the shoulder straps very tight, you probably need a smaller band size or a deeper, more supportive band.
  • Check that the underwires are high enough at the sides to support most of the cup. Imagine a line connecting one end of the underwire to the other. The area under this line will be supported by the band, so if the centre of gravity of your breast is above this point, a large proportion of the weight will have to be taken by the straps. This is why plunge bras often seem to weigh down more on your shoulders, and why strapless bras are usually full cup styles.

Signs that you’re wearing a well fitting bra:

  • Your breasts feel supported from your chest rather than your shoulders.
    The cups are a perfect fit, with no wrinkles or bulges.
  • The underwires surround the breast, not sitting on or digging in to any breast tissue.
  • The band is a snug fit, tight enough to offer support. It fits on the biggest adjustment when you first buy the bra.
  • Your bra doesn’t weigh down on your shoulders, leaving painful red marks.
  • You don’t have to be constantly adjusting it.
  • You feel your posture and silhouette are instantly improved.
  • Your clothes hang better, as your bustline is lifted to the correct level.

Remember – the fit of your bra is more important than the size you get from any measuring formula. At the end of the day, the correct size is the one that fits and does its job.