16. Dear Gabby: Increasing Cup Sizes — Help!

Dear Gabby,

I would love to make a bathing suit top, but all the patterns seem to be a C/D cup, and I am a G cup. How do I grade bigger cups? I have the Seamwork Reno pattern, and the Closet Case Sophie, which are both C/D cups from what I can find, and my bra size is 34 G.

Sincerely, Natural Knockers


Dear Natural Knockers,

Luckily, both of the patterns you have have great design lines, that will make it easy to increase the cups.

First, you’ll want to increase the total cup length and width — you’ll need both to fully cover the breast, if you are going from a D to a G.  This means you’ll need to increase *each piece* proportionally to get the total increase, and to maintain the design look and style line placement on your body.  This will require some experimenting, due to the differences in shapes between the two styles.  One thing to remember — whatever you change on the self pieces, don’t forget to change the lining as well!

*A note: unless you are grading between pattern sizes on the pattern, I don’t think you need to worry about what a traditional cup grade looks like. I would go from what the pattern is directly to what you are, it’ll save a lot of time and stress.  Different brands have different cup sizes and different grading, and this holds true to pattern companies too: what one person may call a G cup, another may call an F — irregardless of standard measurement ratios.  Different sizing, different grading, different shaping, different fitting — it’s enough to make a person throw their boobs up and walk away! But do not worry: you are not the problem, the problem lays in inconsistencies in sizing practices and the lack of extended sizing availability. You are sewing custom, and it really just matters what fits and works for YOU.

Here are two methods to find out how much to add:

Gabby's sketch showing the different pattern pieces for the bra or swim top, and where adjustments might need to be made for each piece.
Expand the image for my suggestions on where to get started with the Reno!

1.  If you have a swim suit with a similar cup, or even a similarly shaped bra, you can measure it (cup height and width), to get an idea of how much total you’d need to increase the cups.  If you’re having trouble measuring flat, put it on and measure! Then you can compare back to the existing patterns. Ideally, this is something that already fits you well — if you don’t have anything on hand, you might want to go try some things on in a store and measure what fits.  (You don’t necessarily need to purchase anything, if you’re just looking for shape reference.  Remember on Project Runway, when the twins got in trouble for sneaking measuring tapes into the fitting room?  Well… let’s just say this isn’t a reality competition show 😉  

2.  I’m always a fan of making a muslin. Use some fabric that’s similar to your chosen fabric, but nothing pricey, and you can mark/cut/pin it as much as you need!  A technique that’s very helpful for me when working with knits is cutting the muslin where it’s obviously tight, and then using larger safety pins to hold the cut together as it’s relaxed, so you can see how much you need to add.  Sharpies, scissors, and safety pins are all your friends. Just be careful!

Gabby's sketch shows the sleeve of a fitted tee, with a slash reaching almost from shoulder to hem, and safety pins across the opening to control the spread.
Quick sketch of how to pin a cut muslin.

Here’s a fascinating video from Diane Deziel on bra cup grading. This will give you an idea of how to increase the pieces.  The measurements will be different, but I like how she shows how to use the pattern piece itself to create the graded version, so the shaping stays true to the design.  This can be a bit complicated to follow, however, so you can always use the good ol’ slash and spread method, and reblend the outer lines accordingly. 🙂

Additionally, CCP has a fitting guide for the Sophie here.

Bra cups can be a pain in the butt — or breast, really — but they don’t have to be. Perennial advice from me: measure your patterns, measure yourself, and look at style references!


Got questions? I’ve got answers! And if I don’t, please allow me to google it for you…

How to submit:

Email gabby@starislandxo.com.

Send an explanation of your problem with a short video or set of photos, and your contact information. Your submission will be edited into a blog post, so please note that by sending an email, you are granting permission for your video/photos and sewing problem to be shared online. You are helping the community see all-bodied individuals! There is no shame or judgment — the end goal is to help you *make* clothing that feels great and that helps you *feel* the same way while wearing it.

See more here.

xo gabby


Gabby is a technical fashion designer, fit specialist, and prolific googler. She lives in Denver, raises tiny littles, reads, embroiders, makes, experiments, fails, learns, tries again. See her on instagram @ladygrift.


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