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How To Make A Bra 1

icon free“I must, I must, improve my bust”

This is my first article on bra pattern drafting (drawing) and construction. But for this article you do not need to get out the sewing kit and fabric just yet, as we need to sort out one main problem: what size bra do you want?

Almost every day, bra companies and fashion magazines declare that 70% of women are wearing the wrong sized bra. I believe that this is a nonsensical statement, as we have no standard breast measurement and size labelling system that is recognised around the world, and many women are happy and comfortable to wear their “wrong” sized bras. In writing articles about bra pattern drafting and construction for a website that has followers from around the world, we must first overcome a worldwide problem:

“What is my bra size?” 

When a designer produces a new bra for the British market, the prototype is made to a “core size”. In Britain this would be a UK 34B (even though the average bra size in Britain is now about 36C/D). This prototype is then “graded” (enlarged or reduced) to produce the other sizes.

But a British 34B size bra can also be labelled as

  • 34A in the USA
  • 75B in Europe and Japan
  • 90B in Spain, France and Belgium
  • 2B in Italy and the Czech Republic
  • 12B in Australia and New Zealand.
  • B75 in Japan

And to make matters worse, the identification of cup size by letter is not consistent across the globe: 

  • UK: AA-A-B-C-D-DD-E-F-FF
  • UK specialist: G-GG-H-HH-J-K-L
  • American: AA-A-B-C-D-DD-DDD
  • European: AA-A-B-C-D-E-F

The EN 13402 industry standard - AA, A, B, C, D, E, F, G, H, I, J and K - will eventually help resolve the current confusion surrounding cup-size codes, but only in Europe.

As well as no standard bra size classification systems, the antiquated way in which women are measured for a bra is far from satisfactory, as it does not take into account the volume of the individual breasts and the variations in back size.

You know the drill: for UK sizing, measure in inches around the chest just under the breasts, then add 5” if the measurement is an odd number or add 4” if the measurement is an even number. This is your “Band size” - 30, 32, 34, 36 and so on.Determining your band and cup size Now measure around the bust at its fullest part and take the band measurement (+5 or +4) away from this measurement. The difference - 1”, 2”, 3”, 4” - indicates your cup size.


  •  29” + 5” = 34” band size
  • 34 back size and 35 full bust is a  +1” difference  = B cup

Think about this measurement method applied to two body shape extremes.

  • A woman who measures 29.5 inches around her ribcage and 35.5 inches around her overbust, but has a narrow back and full breasts.
  • A woman who measures 29.5 inches around her ribcage and 35.5 inches around her overbust, but she has a muscular, wide back and small breasts.

Using the traditional measuring method, both of these women would be offered the same size bra, but they have significantly different body shapes.

So for the bra pattern drafting and making articles I will use a simpler and more accurate bra cup size identification and measurement system. More on that later.






Parts of a typical Bra.

So that we are all “singing from the same hymn sheet” and you know what I am referring to when I am writing about bra pattern drafting/construction, here are the parts of a typical bra.

Parts of a Bra

By the way, in the industry a garment pattern that you are working on to change the style or size has no seam allowance and is called a “Block”. When you have made all the changes, you then add the right seam/hem allowances.



The big headache about bra pattern (block) grading.

When we want to change the size of a bra pattern/block we could draft a new block for the new size, but in the industry a single “core size” block is “graded” (adjusted) to produce the other sizes in the range.

Take, as an example, the British bra size system. There are 16 cup sizes, AA - A - B - C - D - DD - E - F - FF - G - GG - H - HH - J - K -L, and 6 band sizes from 30” - 40”. That makes 96 size options. Multiply that by 2 colourways (ie making white and black bras), and you and your company potentially have 192 different bras to make!

BUT what if you could use parts of one size bra in a different size bra? You can!  Welcome to the world of bra CROSS GRADING.

If you take the cups and the cradle/underwires of a 34B bra and shorten the wings by the right amount, you have a 32C bra! Likewise, if you lengthen the wings on the cups and the cradle/underwires of a 34B bra by the right amount you will have a 36A bra! The same goes for other Cup/cradle sizes: - the cups/cradle of a 38D bra are the same size cups/cradle as a 40C bra, and 36DD bra and a 34E bra, and so on and so on.

The tabel below shows cross grading using EN 13402 standard cup lettering.

Same cups and cradle





Same cups and cradle





Same cups and cradle






Same cups and cradle






Same cups and cradle







Same cups and cradle







Same cups and cradle







Same cups and cradle







Same cups and cradle







Same cups and cradle







This cross grading system is also used for bra underwires: the underwires that are used in a 34B bra can also be used in a 36A bra, and so on.


Size/band grading

The standard step increase in band size is 50mm (2"), which takes a 34B to a 36A, for example. (Some European brands use a 40mm underband increase instead, which can result in a much smaller and tighter fit in large band sizes.) The underband will increase by 50mm; a quarter of that increase must be placed in each half cradle and wing, as shown in the diagram below.

 Classic 50mm Bra Grading




Cup Grading

To get from 34B to 34C, for example:

  1. The underband length remains the same.
  2. The cradle must increase to provide the larger cup size, but the wing must get smaller to maintain the underband length.
  3. The cup section is graded one size larger.


Darted Bra 50mm Grading Rules.

So here are the three grading principles for bras.

  • Cup Grading: - to increase the cup volume, the cradle of the bra must also increase to accommodate the increase in cup size and the wing must be reduced to maintain the band size.
  • Band Grading: - to increase the size of the band, but maintain the cup/cradle size, (eg 34B to 36A, or 34B to 36B) combined with cup grading.
  • Cross Grading: - to use the cups and cradle of one size as the cups and cradle of another size bra (eg 34B cups and cradle used for a 36A bra).

Darted Bra Grading

When we draft (draw) the bra pattern, we will do some grading to make the cups and underband to your size. The manual method of grading bra patterns that we will be using is called “shift grading”.

It uses vertical and horizontal axis lines, which must be at right angles to each other on each pattern, or “star” lines radiating from a “Cardinal” point. You can do the pattern and grading on a computer if you have a good “Vector Line” drawing CAD (Computer Aided Design) program such as AutoCAD, Corel Draw or Adobe Illustrator. I personally use Corel Draw.

That’s enough of the world's sizing problems; we need to get on with the stuff that you need to know to make a bra.

So what is your size?

I mentioned that I would employ a different measurement and sizing method for these articles. So get out your tape measure and take all measurements in CENTIMETRES (sorry America and Britain, it's metric all the way from here). Write all the measurements down. If you're not making your own, and you don't have a particular client, family member or friend in mind, then use the measurements for a “Size 4 cup” and a “50cm back” (equivalent to a UK 34B core size). 

When taking all measurements, try to be as accurate as possible (to the millimetre).

The first two measurements you need to take are your “Over Breast” measurements, from the “breast root” at the side to the “breast root” at centre front. Your “breast root” is the line where your beast joins the chest wall and where the wires of a correctly fitting underwired bra should sit. When taking the measurements you should wear a good fitting underwired bra that lifts the breasts up into the fashionable full shape; the underwires in the bra should help you to identify your “breast roots”.

I know it’s a “Chicken or Egg” situation - to take measurements to get a well-fitting bra you first have to be wearing a well-fitting bra! But I am still working on a simple way to get the dimensions/volume of clients' breasts without going to a local hospital and using their MRI body scanner. 

Take the measurements horizontally over the fullest part of the breast from the “breast root” at the side to the “breast root” at centre front. Measure both breasts, then use the larger measurement. Do not worry if the two breast measurements are different, no-one is perfectly symmetrical.

Measuring over the breast Measure from wire to wire, if wearing a good fitting bra

Now refer to the table to find your cup size, and make a note of it:

Over breast measurement Cup size Over breast measurement Cup size
14.1cm to 14.7cm 1 45.1cm to 46.8cm 16
15.8cm to 16.4cm 2 41.3cm to 41.9cm 17
17.5cm to 18.1cm 3 43cm to 43.6cm 18
19.2cm to 19.8cm 4 44.7cm to 45.3cm 19
20.9cm to 21.5cm 5 46.4cm to 47cm 20
22.6cm to 23.2cm 6 48.1cm to 48.7cm 21
24.3cm to 24.9cm 7 49.8cm to 50.4cm 22
26.0cm to 26.6cm 8 51.5cm to 52.1cm 23
27.7cm to 28.3cm 9 53.2cm to 53.8cm 24
29.4cm to 30.0cm 10 54.9cm to 55.5cm 25
31.1cm to 32.8cm 11 56.6cm to 57.2cm 26
33.9cm to 35.6cm 12 58.3cm to 58.9cm 27
36.7cm to 38.4cm 13 60cm to 60.6cm 28
39.5cm to 41.2cm 14 61.7cm to 62.3cm 29
42.3cm to 44.0cm 15    

So if you measure 19.6cm over the fullest part of the breast from the “breast root” at the side to the “breast root” at centre front, then you will draft/grade/make a size 4 cup. If your over breast measurement is between·two cup sizes, go for the higher cup size.


Measuring for the band measurement

The Back/Band Measurement

Again, locate your breast root at the side of your breast, take the tape measure around your back horizontally to your breast root at the side of your breast on the other side. Make a note of your Back/Band measurement.

Now we're ready to begin drafting in the next article.


An extra note to all the mathematicians out there: have a think about how you would determine breast volume and the dimensions to put that breast volume in a fashionable shape...


Click here to go on to part 2 of the "How To Make A Bra" series

Jean Gormley  
  Great website, cant wait to
  I have been doing a little research about bras and i came up with a formula, to put "put breast volume into a fashionable shape" Will you be willing to help me test it.  
Dawn Mason  
  lolLooking forward to the next part.As I am allergic to so much in bras I have to wear ugly white cotton sports bras which do nothing for my self confidence .  
Shirley A. Stanley  
  Don't laugh before you think carefully about it. How about trying "water displacement" as a means to measure breast volume? I know it would be really awkward, but might it possibly be "doable"? It would certainly be less costly than the local hospital MRI machine. To do this, a container (bowl, whatever) containing a known volume of water would be placed on a firm, waterproof surface. The breast would be submerged, being careful to submerge all, and only, those parts of the breast intended to be covered by the bra cup. Of course, this breast mass would make a corresponding volume of water leave the bowl. Then, once all had settled, the breast is removed and the remaining volume of water in the receptacle measured .  
  That's exactly the method I've been considering; I think it's a great idea!  
  I was thinking along lines. thing is water displacement is easier calculated with putting the first bowl to a pot with scale outside it if you don't want to get low precision. or possibly have the first pot have a scale. By the way anyone has any idea how to create bra like structure by crocheting in crochet corset(well corset look a like , it doesn't have to actually shape body just be well fitted)? I intend to make wedding dress by crochet and advice would be valuable as my design calls for all to be continuous ( having least amount of individual pieces of crochet stitched together as possible). I think I could try to make it as one part with rest of dress but I won't have it flattening my girlfriend because she would hate it  
Sharon Redmond  
  I took my cup measurement and it is 59 which is not listed on your chart. What do i do now?  
  Hi Sharon Redmond
I will put up an extended cup size table shortly, but in the meantime think about “Grading Steps”. The step between each cup size is 1.7cm and the grading steps for the line lengths are at the top of the table.
Will be as quick as I can with the table.
Corset Hugs
Amanda Boissoneault  
  Mark, when you talk you sound like Dave, a teacher who teaches bra drafting at DMU, Where you his pupil at one time? Very well written instructions. When I went to learn to draft plus size at DMU we took 34B which became very distorted in grading. It was odd we were informed not to grade above a certain size and then they weren't practicing what they preached. I had to develop my own formula to eliminate this distortion.(15 grades and no distortion) I really like the math for the dart bra. Never seen it before.  
  Hi Amanda,
So so sorry, I missed your comment when you posted it. Please go to the forum page, Bras section for a full reply
Corset Hugs

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