Bust Cup Sizes

Bust Cup Sizes for Blocks, Patternmaking & Commercial Patterns are not to be confused with Bra Cup Sizes. They may not be the same, and may be very different; e.g. you may be an F cup in bras, but be only a C or D cup for patternmaking.  

How are Bust Cup Sizes Defined?

For the purposes of block and patternmaking, bust-cup sizes are based on the difference between the measurement of your Upper Bust and your Bust.  If you subtract your high bust from your full bust, the difference determines your cup size.

  • 1″ = A cup
  • 2″ = B cup
  • 3″ = C cup
  • 4″ = D cup
  • 5″ = DD cup (or E cup)
  • 6″ = DDD cup (or F cup)

Example Image

In the image, the Upper Bust measurement is 34 inches.  The block for a B Bust cup (blue lines) will fit a bust of 36 inches – 2 inches more than the Upper Bust.  The block for a C Bust Cup (green lines) will fit a bust of 37 inches – 3 inches more than the Upper Bust. The block for a D Bust Cup (the pink lines) will fit a bust of 38 inches – 4 inches more than the Upper Bust.

Note: The image below was updated on 11 April 2019. When I updated the image, I indicated the A cup line that would be used to create the block for a bust of 35 inches, but the A cup block isn’t drawn (i.e. you can see the blue outline for the B cup, the green block outline for the B cup and the pink outline for the D cup, but there is no yellow outline for the A cup block).

The Difference between Patternmaking Cup and Bra Cup

With a bra, cup size is based on the difference between your bust and your under-bust.  In patternmaking the under-bust measurement is not relevant for the Bodice Block; any fitting that needs to be done under the bust can be done by darts or design lines; e.g. an Empire Line can reduce the amount of ease in the under-bust to provide more fitting. If you think if how the fitting of a bodice garments differs to a bra, and their different purposes, it should be clear why the patternmaking cup is different to the bra cup; When drafting a bodice block, you are concerned with the angle that the fabric falls from the upper bust and how this affects how much fabric is needed at the side of the body to accommodate the bust.   The bra on the other hand is about supporting the breasts; the actual support is done by the band, which goes around the under-bust.  The under-bust is therefore an essential measurement in bra construction, while it is irrelevant in drafting a Bodice Block. This image may help you see how the upper-bust to bust measurement is so different to the under-bust to bust measurement. Some people with very large busts in bra-cup sizes (F, G, H), may also have a very large fleshy upper-bust and have only a C or D cup for patternmaking purposes.

Important Notes:

  1. When I created this article, my instructions included 6 inches ease in the Upper Bust.  I have since changed that to 5 inches in the Upper Bust for a Closer Fitting Bodice Block.  The first image on the page still has 6 inches noted.
  2.  Drafting the block with 5 inches ease in the Upper Bust should result in approx 2 – 2.75 inches ease in the Bust.  (The larger your bust cup, the less ease).
  3. If you have tried other block making instructions in the past, you may think that 2.75 inches ease in the Bust is excessive because most instructions add 2 inches ease to the Bust measurements.  However, just because they add 2 inches ease to the Bust measurement does not actually mean that the final block has 2 inches ease in the Bust.  Please see the articles below for examples, where  I have drafted blocks with their instructions and measured the Upper Bust and the Bust when finished.

24 Responses

  1. Hi. This is a great website. A lot of useful information, and very detailed. To much effort and dedication. I want to do a bodice block with your method, but I have a few doubts: my upper bust is 94 cms (37.79 ”)., and my full bust is 98 cms. (38.58 ”), there are difference between both are 1.58 inches. Which cup I have to choose: A cup or B cup ?

    Thanks for any answer or suggestion. Greetings from Chile,
    Ps: Apologize for any writting mistake. I’m spanish spoken person.

  2. Hello Sara, so sorry it has taken me so long to answer, but I have just realised the Comment System has not been advising me when comments have been posted. Just found out that you left this comment a few minutes ago,,,

    If the difference between your Upper Bust and Bust is 4cm, then you are pretty close to a B cup. If you look at the instructions for the Bodice Front, Figure 2, for a B-cup the line E is 1.25 inches (3.175cm) from the C-D line. However, as you are not quite a B cup, you could draw that line at about 2.5cm for a better fit. This will make the dart cup just that bit smaller and better fitting.

    (Note: An A-cup extensión would be at 1.58cm from the C-D line).

    Hope that makes sense. Let me know if it doesn’t. (Also hope you haven’t given up because I didn’t reply).

  3. Hello Maria. What should be done for someone with an A cup. What Would you suggest as an extention of the E line in inches, that is where there is a difference of 1inch from the bust to upper bust

  4. Hello Maria. Thanks for all the information. Please what option is there for someone whose bust and upper bust is the same or where there is just one inch difference. by how many inches will the E line be extended. or will there be no extension at all

  5. Hello again

    See the comment above…. A 1-inch difference is an A-cup – I have updated the instructions to include that.

    In the case where there is absolutely no difference between the upper bust and the bust (a completely flat chest), then I imagine that you would just use the C~D line. In this case you wouldn’t need a side seam dart – darts are for shaping around the bust, and if there is no bust, no shaping would be required. You would still need a waist dart to shape from the chest to the waist.

  6. Hello Sara,

    I just realised that the measurements in this article originally were all over the place (i.e. incorrect!). For anyone trying to understand the concept it would have been very confusing. Just to let you know that I have corrected the measurements in the text and in the image.


  7. Hello Charlie

    I just realised that the measurements in this article originally were all over the place (i.e. incorrect!). For anyone trying to understand the concept it would have been very confusing. Just to let you know that I have corrected the measurements in the text and in the image.


  8. Thanks soo much for your prompt response. My last question on this please. I noticed an increase of about 0.63 between each cup size. Do you suggest I keep adding 0. 63 as I go up in cup size. Like for some one with a difference of 7 inches between upper bust and lower bust, how many inche’s will the distance of the E line. Thankss

  9. Hi, yes I would think so… Having said that, I’ve never made a block for anyone with a G or H cup, but the theory should hold.


  10. Hello Maria,
    Thanks a million for your response. i really appreciate. i just have one last question on this and i
    promise not to bother again. i noticed an increase of about 0.63 inch between cup sizes. would you suggest i add 0.63 as i increase cup sizes. for example a difference of 7 inches between upper bust and bust should i keep increasing by 0.63. thanks again

  11. Dear Maria. thank you for this website, it is giving me many answers to my questions regarding the pattern making.
    I came to one situation while trying to follow your Bodice Block instructions and it relates to Cup sizes… I am exactly between DD a DDD size (5.5″). Do you recommend to put E line just in the middle of DD and DDD line? does experience say to rather choose smaller/bigger size instead?
    thank you very much for your advice…best regards from Prague… Henrika

  12. Hello Henrika,

    I suggest you make a 1-Dart Bodice Block, and draw both those (Cup) a lines as the side seam (see attached Image A). When you make your toile, draw all the measurements lines on your toile. (see Image B – Although this image is of a PANTS Toile it gives you the idea. I can’t find my Bodice toile example at the moment.)

    Draw both of those side seam lines (with a non-bleeding texta or just a pen). First sew the toile on the larger Bust line and check the fit. Then unpick the side seams and sew on the other line and check if that is better. The Waist dart will be bigger if you use the larger Bust-Cup line, but to begin with don’t sew the waist dart in at all. Just check which side-seam line works best for the fabric over your bust, then you can work out the waist dart from that.

    It is better to check it out what works best for you. Some people like more ease than others.

  13. Hi Maria. thank you for your advice. I will try both cup lines as you recommend. my single dart is huge already with DD cup so I will have to split it later on anyhow to be able to sew it. so it means multiple toilets to try. but I believe that it’s still worth it as no purchased pattern nor RTW cloths fit my upper half of the body.

  14. Hello again Henrika

    Yes, one dart will be far too large for general use. I suggested using the 1-Dart Block because it makes it easier working with those 2 options for the side seam – purely for the purpose of that first toile to get the Upper Bust/Bust proportion and fit right. Once you have determined the correct side seam, I suggest you then make a 2-Dart Block.

    There are instructions for making a 2-Dart Block from a 1-Dart Block…..

    Or, if you made the 2-Dart once first, you can make the 1-Dart Block from that one:

  15. Hello again Henrika,

    It took me so long to get my blocks just right, but it really was worth all the effort. A lot of ready-to-wear clothing seemed to be instruments of torture when I had to rely on ready-to-wear clothing. It is so wonderful to be able to make clothing that fits me well and is comfortable.

  16. Dear Maria
    so I tried my first toile over the weekend with DDD measure for E line. it seems to fit in the underarm, actually I have a lot of ease there while it still pulls in between bust level. if I would made button closing in the middle of front bodice, pull will be visible there while I will have enough ease in underarm and too much ease between shoulder and bust level (looks like 3cm dart to armhole is still needed). I haven’t attached my sleeve yet so I’m not sure how it will behave with sleeve sewed in. I keep on trying 🙂

  17. Hello Henrika, It’s late at night here and i’m reading my ipad in bed. I say this only to explain I don’t have my computer on or my access to my graphics… But I will start with a 2 questions….

    I would check the following..
    1. Are you measuring your Upper Bust correctly
    2. is your armhole depth correct?

    Attached find a photo of my mannequin as example….

    I will be going to bed now so won’t be answering again tonight, but please let me know.

    If you are taking these measurements correctly, could you send me a photo of the toile on you and all the measurements you are using?

  18. Hi Maria,

    This is an incredible resource. Thank you so much! I’m going to have a go at building a block with this in the coming week. Like you I’ve been frustrated with patterns and have lost my desire to see because of it. I’m actually 6 inches different between my high bust and bust. So I think that makes me an f cup in dressmaking. Would I need to take the e line out further? If I have a go at making this up would I be okay to send some pics to you for your expert opinion? It sounds like you’ve been through the mill with it and I feel your energy 🙂

  19. Hi Rehanon

    Hello Rehanon,

    Welcome. If you are 6 inches bigger in the bust than in the Upper Bust, then you would be an F cup for patternmaking. You would draw that E line 3.78 inches from the C~D line (0.63in per cup size, therefore 0.63 x 6)).

    I am attaching a graphic with some comparisons for your information.
    No.1. is the Standard Block with a C Cup
    No.2. is My Block with a C Cup (I lost weight and went down a cup size)
    No.3. is My Block with a C Cup in blue on top, then underneath (the yellow peeking out) is an approximation of what it would look like if I drafted my block with an F Cup. (Both together for Comparison Purposes).
    No.4. Is my Block drafted with an F Cup (an approximation).

    This is just to show you what an ‘F’ cup looks like. Basically if your bust is bigger then there is more Centre Front Length, a bit more fabric at the side, and a bigger dart.

    So yes, easy enough to draft your block to your Bust Cup. The hardest part of drafting your own block is getting your measurements correct.

    Let me know how you go. Feel free to take photos of your block and post them in the comments if you run into problems.

  20. Hi, Maria. I want to thank you for the library of information you’ve provided. You’ve helped me a lot.

    I hope I’m not commenting too late, but I’d love it if you could help me out here. I’ve noticed that you have different locations for each apex with their corresponding darts (e.g. B cup dart’s apex is highest, C and D cups are shifted slightly lower and to the left). Could you possibly explain why that is?

    I’m trying to make a bodice block for a C cup but I’m using a standard size chart, so not my own exact measurements. My chart has one apex (bust span/bust depth) location. For standard sizes, if I were to make a block for a C cup, does that mean I should be shifting the apex location slightly lower and to the left? If so much? Would you say approx. 6mm down and to the left is a good amount?

    P.s. I apologize if you’ve already explained this somewhere and I just missed it.

  21. Hi Anjela

    As the bust gets bigger, it requires more fabric to cover it (in length and width)…. So, for example, a B cup might have a CF length of 13 3/4, the C Cup will be 14 and the D Cup 14 1/4. (So 1/4 inch is reasonable in regards to the CF length).

    Similarly, as it gets larger the Bust Point moves out and the bust depth also moves down. Generally the bigger the bust, the lower the bust depth.

    I would suggest increase in CF of 1/4 inch per cup size.
    increments of 1/4 inch for bust depth
    increments of 3/16 for the bust span


Leave a Reply

Your email address will not be published. Required fields are marked *