22 Jun 2016 • • by Heather Lou

Choosing a Size and Increasing Cup Size for Sophie Swimsuit

Choosing a size and increasing your cup size // Sophie Swimsuit pattern // Closet Core Patterns

Thank you so very much for the truly awesome response to our new pattern, The Sophie Swimsuit! The studio is currently covered in swim lycra and piles of underwires everywhere and and we'll be shipping out the first batch of swimsuit fabric kits later this week. In the meantime, I thought I would talk about how to choose a size and underwire for Sophie since this is a question we're getting a lot. I'd also like to explain how you can make the pattern fit you even if you fall outside our cup range (which goes up to approximately DD).


Unlike all of our other patterns, you choose your main size for Sophie based on your under bust measurement. This dictates the size you are going to print, even if your waist and hip are smaller or larger.

Size-Chart copy

Your cup size is determined by the difference in inches between full bust and under bust. For example, if your full bust is 36" and your under bust is 32",  the difference of 4" means you require a #4 cup.


(The reason I choose not to letter the cups is simple; based on the way our sizing model works, many people may find themselves needing a cup size larger than what they are used to when buying bras. I didn't want you to freak out if you're a DD in my pattern, so we just want with non-value laden numbers).

Adding additional back support // Sophie Swimsuit pattern // Closet Core Patternsx


Since the one piece View A body has 5 cup sizes, we had to split up the files by individual size or else it would have been a complete nested mess! However, we've nested the waist/hip lines three sizes above and below in light grey so you have some guidelines for grading between sizes. If you need to grade more than 3 sizes for the one piece, I would suggest using the high-waisted bikini bottom as a tracing guide since those pattern pieces have all 11 sizes nested normally. Here is how you would grade between sizes if you were a size 6 underbust/#5 cup and a size 12 hip. As you can see, it's not too complicated to connect from the size 6 at the bust to the larger size at the waist. Your cup pieces aren't effected, just the body pieces. You'll have to grade both center and side panel pieces.

Grading Between sizes // Sophie Swimsuit Pattern // Closet Core Patterns


Although this pattern can be made without foam or an underwire, if you're a #3/C cup or over, you'll simply get a better fit with the added structure. We are including an underwire in the swimsuit fabric kits and I have a guide to finding your size on the shop, but I thought I'd explain it here too, especially if you're planning on buying your underwires from another source. Sophie was drafted around the regular length wires from Bra-maker's Supply so I suggest getting underwires from there if you don't want to trim them down (I've noticed that the wires they sell are slightly shorter than in their sizing chart which is what we used to draft the pattern - you may want to get a pair of long wires too, and see what fits better in your channel).

Cup sizing can be a little confusing the first time you dip your toe in. As I mentioned above, you find your cup size by subtracting your full bust from your under bust, with every inch difference representing a full cup size. However, not all cup sizes are created equal. For example, the actual volume of a B cup on a woman with a 30" under bust is much smaller than a B cup on a woman with a 38" under bust - in both cases the difference between full and under bust is 2", but the woman with a 40" full bust naturally has more breast tissue than one with a 32" full bust.

Underwires measure the quantity of that breast tissue, or the diameter of the breast itself, and the most common kind is numbered from 30-60. For every jump in cup size, the number of the underwire goes up 2 in size (ie. 30, 32, 34, 36, etc.) Let's take a look at my underwire chart to see what I mean.


You can see that as the cup size increases with the chart moving right, the underwire number goes up. You may also notice that size 0 & 2, 4 & 6, and 8 & 10 share the same underwire sizes. Don't worry too much about this; it's just how we had to make a cup sizing model work with our existing sizing system, so some of our underbust sizes share cup sizes as well.


To find your underwire size, find your underbust size in the left column and then the difference in inches with your full bust along the top. Where those two lines intersect is your underwire size. For example, a woman with a 31" under bust and a 3" full bust difference would take a #36 underwire. If she had a 4" difference, she would take a #38 underwire, a 5" difference a #40 underwire, and so on.


If all of this is too confusing and you feel pretty confidant that you're wearing bras that fit you well in the cups, you can  also choose a cup size based on your existing bra size. To do that, print out this underwire chart from Bra-maker's Supply at home with no scaling. Lay your underwire on top of the chart until you find one that matches in size, and then use that underwire/cup size for your swimsuit!



Grading this pattern was a bit of a feat, so although I wanted to offer a bigger range of cup sizes, it just wasn't possible to grade nicely. However, it isn't hard to go up cup sizes. What you need to do is figure out what your underwire size is. Remember that every inch difference equals a cup size, and that each underwire size goes up by a factor of two. So, if your underbust is 31" and your full bust is 37", that 6" difference means you would require a #42 underwire (one size above the #40 required for the 5" difference). Looking at the chart you can see the #42 underwire is used for the size 12/cup 5. You would therefore need to use the cup pieces from the size 12/5 cup and then trace off the cup opening from that size onto the size 10 body.

To do that, line up the size 12 body over the size 10 body - you can use the grey "grading lines" as a guide. The line in blue below shows the size 12 on top of the size 10.

Grading cups up 2

You would then simply trace off the size 12/cup 5 bust line onto your size 10 body. That is shown in red below.


The principle is more or less the same for the bikini top, but if you're only going up one size around the underbust you can probably just get away with making the size up and then adjusting the length at the center back if necessary.

Support wise, I will say that the bikini top is definitely more supportive than the swimsuit. The band really anchors everything into place around the ribcage. If you have a very large bust and would like to make the one piece, you may have to sew in some sort of concealed band support along the back of the suit to help provide enough support to the front. One of my lovely testers constructed this powernet & elastic back band and she said it worked really well:

Adding back band support to Sophie Swimsuit pattern

Hopefully that clarifies sizing for this pattern. Feel free to hit me up with any questions in the comment section!

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