Bra's and Breast Size



The bra or brassiere has a long and convoluted history that goes back to a least Roman times - and probably far earlier.  There are many claims as to when the modern bra appeared, but I think the American advert below from 1934 shows a strong contender. 

Every woman with breasts - regardless of whether she is a mature CIS-woman or a young transwoman taking hormones - can benefit from a well fitting bra.  The benefits are numerous but the most important are  appearance, comfort, reduced back strain and reduced sagging. 

Just how great these benefits are in reality is the subject of much argument, with the context that Homo Sapien women survived without bra's for maybe 200,000 years.  There is also some conflict - a women with large breasts may prioritise comfort, whilst a woman with small breasts may prioritise appearance.  However few women would voluntarily give up their bra.  This page makes the assumption that a well fitting bra is a good thing, and that a badly fitting bra is ... well ... a bad thing.

It will be of no great surprise to readers to learn that a woman's breasts come in all shapes and sizes.  Breast size and shape is most commonly described using classifications developed by the lingerie industry and brassiere manufacturers.  Unfortunately these "standards" are often confusing and far from consistent.   The guidance below is intended for women in the UK and Ireland, but much is applicable more widely.


Measuring Your Bra Size
To determine your correct bra measurements, as used by most (although confusingly far from all!) foundation garment manufacturers:

A) Determining your Bra Size

  1. Use a cloth measuring tape directly under the bust, checking in a mirror to make sure that the tape is straight across back - this is the "chestband size". 
  2. If the chest band size is an odd number add 5 inches, if it's an even number add 6 inches. Note the measurement, it's your actual frame size.
  3. Measure around the chest at the fullest part of the bustline. The measuring tape should be held horizontal (check back in a mirror), and your arms should be down. Make a note of the "bust size" measurement and compare it to the Bra Size from step 2.
B) Determining your Cup Size
  1. "Cup size" is a measure of the volume of the breast, and is denoted by the first letters of the alphabet.  Bra cup size classification is as follows (going from smallest to larger):  A, B, C, D, and DD (also known as Double D or sometimes called E), etc.  To determine the proper Cup Size, find the difference between step 3 and step 2 (i.e. bust size - frame size)  Use the chart below to determine your cup size.
Chart to Determine
Bra Cup Size




Cup Size

Step 1: Chestband measurement is 31". Add 5 inches. Frame Size is 36.
Step 2: Full bust measurement is 39".
Step 3: 39 - 36 = 3" difference. Cup size is C.

Result: Buy a 36C bra.

Half inch
One inch
Two inches
Three inches
Four inches
Five inches
Six inches
Seven inches
AA cup
A cup
B cup
C cup
D cup
DD or E cup
DDD or F cup
FF or G cup

  • Also available are training bra's which are roughly equivalent to size AA.  These are made from stretchable materials and especially designed for supporting the rapidly expanding breasts of prepubescent girls.  Training bra's are also very useful for transsexual women who have started hormone treatment, but unfortunately training bra's are very rarely available in the shops above frame size 34 and the largest I have found on the Internet is a size 36 from brafitters.com (this is not a recommendation, I have never used the company).
  • Although uncommon, the large cup sizes of H, I and J also exist.  These bra sizes are [obviously] needed by very large-breasted women, or women whose size increases substantially with pregnancy and nursing.  
  • For sizes DD (aka E) and above, accurate measurement can become difficult and great care must be taken to ensure a proper fit. 
  • Women whose actual under bust chest band size is over 33" should always try reducing their frame size by one size, i.e. if they calculate they needed a 40B bra, a 38B bra on the last hook may well prove to be a better fit.
  • Annoyingly, some bra manufacturers deliberately make their bra slightly large in order to flatter the potential buyer, e.g. a bra marked 38C may best fit a 40B woman.
  • Many garment manufacturers recommend that bra size measurements should only be taken while wearing an existing comfortable and unpadded bra that fits well.
  • If you are taking these measurements for use with breast forms (prostheses) you can simply take the frame size measurement (Step 2) and then choose the cup size that is right for you.
  • Long line and 3/4 bras should only be considered if their length is LESS than the distance from the under bust to the natural waist line.

A properly fitting bra is crucial to your best appearance. A bra that fits correctly will touch your chest at the sternum and support your bosom at mid-chest without bulges. 

Badly fitting bra
1. Straps digging into shoulders.  Go down a band/back size.
2. Breasts bulging over the bra.  Too small, go up a cup size.
3. Bra rides up at the back.  Too big, go down a band/back size.
4. Front of bra sits away from chest wall.  Go down a band/back size.
Well fitting bra
1. The breasts are smoothly enclosed in cups with no bulging.
2. The front of the bra lies flat against your body.
3. The bra is firm but not tight and leaves no red marks on your body when taken off.

A well fitting bra should have:

Good support: cups that fit all the way around each breast and keep them from sagging, straps that don't have to carry so much of the weight that they dig into your shoulders, not only permanently indenting them but adversely affecting circulation to and from the arms. One factor is choosing wide-enough straps, so they're not so thin that they cut, another is a properly fit cup. 

Good coverage: modesty is an influence in how the cups should fit, with the exception of some deliberately immodest cup styles. Halters and bathing suits come to mind here, because they're outer garments and must be made more modest. Always be thinking about not only your audience, but whether this garment is to be used as an outer garment. 

Snug-enough chest band: this should not, as with straps, dig into your flesh, it should be snug enough to still be snug enough at the end of a long day, but not bind and dig.  When the chest band is too snug, it also draws the underwire into your ribs and will bend them along the lower cup side or the bottom, digging them into your ribs.  By the end of the day, this has been shear torture.  The band should fit well enough not to slide around long your chest.  If you can put the band on backwards and slide it round your chest to the front, it's too loose.  Wear a smaller size or use the next-smaller row of eyes. 

Underwires that don't poke: if the underwire is poking under the arm it may be too long, a possible solution being to find or alter a design in which the cup side is a little lower, or use a slightly less deep (maybe by nipping and retipping) wire in that style or pattern of bra.  Also, if the cup side seam is too far forward, as with a too-small cup size, the wire will poke your arm, even more so if it's too deep.  This can also result from a wire that's too wide, moving the tip too far under your arm and poking you.  If the underwire at the centre front does not lie flat, but comes out at an angle from your body or curves or is anything but vertical along the chest wall at centre front, it's not right.  Adjust the straps, or find a style or size of bra in which the centre front ends of the underwire will lay flat against the centre of your chest and be snug enough, with enough cup room and support to be comfortable and effective without digging or sagging, poking or bulging anywhere.

To see if your bra is suited to your bust type (low, high, full, etc.), try this test: Stand in front of a mirror. Tie a string around your waist. Hold something straight (like a yardstick or even a pencil) horizontally at your collarbone (the two bones at the base of your front neck).  The fullest part of your bosom should be no lower than mid-chest level, halfway between the string and the stick.  If your bosom is closer to your waist, you need a bra that will lift your bosom. (Many women think they are short-waisted when they are just low-bosomed.)  Next, place your finger on the cleavage area of your bra and press.  You should not be able to bounce your finger in and out; if you can, your bra cups are too small.  Then feel along the front edges of your bra and down the seam under your arm.  Are there any bulges?  If so, you need a larger cup.

The photographs below show examples of varying breast and cup sizes.

Cup Size: AA

30 AA

32 AA

34 AA


Cup Size: A

32 A

34 A

36 A


Cup Size: B

30 B

32 B

34 B

36 B


Cup Size: C

30 C

32 C

34 C

36 C

38 C


Cup Size: D

34 D

36 D

40 D

42 D


Cup Size: DD (E)

36 DD

38 DD

40 DD

42 DD

Breasts are usually asymmetrical, meaning that one woman's breast may be a different size or shape than her other breast.  Interestingly, a woman's left breast is usually a little larger then her right breast, though this is only a generalization.    The woman shown has a left breast that is larger than her right breast, in fact, many of the photos above show breast asymmetry. 

Inverted nipples are also quite common and are not a problem unless they cause difficulty during nursing.  Special nipple cups can be used to help during lactation.  A nipple that previously was not inverted but then became inverted is a warning sign of breast cancer and needs to be brought to the attention of a doctor:


Atlas of Cup Sizes

Just for fun, the image below (sourced from a German magazine) claims to show the average bra size of women around the world.  I suspect that it is very inaccurate!



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Last updated: 25 November, 2001

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