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Finding the Right Size (Bra Cups)

I am super excited that Amelia Lane Designs started carrying notions! They hardly take up any room in a box, so I can fit lots into my already fabric-stuffed box. If I ordered from someone else, I would have to pay a separate shipping fee. Plus I know the bosses at ALD have vetted all the products (so they're not junk!) and I like using ALD so that the Facebook Group can be there to support me.

I always seem to need swim elastic and I'm glad to have S hooks readily available because of my newest patterns calls for a couple (plus these are coated S hooks so they don't break or burn).

I am also excited about the silicon backed elastic for making power bra straps and also because I'm thinking about using it around the top of the bodice for extra support to hold up my next off-the-shoulder formal dress come this year's ball. All of these are in the notions section of the website.

The notions section also carries cups for swimsuits and sports bras. One question I see come up a lot is ordering the right size bra cups. I did some research and here's what I've put together!

Assumption: use my sewing cup size. FALSE

I have my sewing hat on when I'm thinking about ordering bra cups, so I'm thinking sewing cup sizes.

Sewing cup sizes are the difference between your upper bust measurement and your full bust measurement.

Upper bust – measure just under your armpits, across the top of your chest. This should be a fairly snug measurement.

Full bust – measure across the fullest part of your chest, wearing your usual bra.

Subtract your upper bust from your full bust.

Mine is about 46.5″-42.5″ which is right about 4″ in my usual bra.

1″ = A cup

2″ = B cup

3″ = C cup

4″ = D cup

5″ = DD cup

6″ = DDD cup

...and so forth

So for the purposes of talking about patterns (e.g. this pattern is drafted for a B cup), I am a D cup. I may or may not wear a D cup bra because bra sizes are not taken using your upper-bust measurement.

Only if your upper bust and under bust are the same size will you have the same sewing cup size and bra cup size.

For sewing patterns you for sure want to be using your upper bust because that's the size that will drive whether the shoulders and chest of your garment fit. Select the pattern size based on upper bust and consider doing a full bust adjustment if your sewing cup size is larger than the pattern is drafted for.

Assumption: So it's just my store-bought bra size? Probably also False

The thing about store-bought bras is that the materials stretch out over time, especially the band, so the bra you're wearing may no longer be the size on the tag. And if that bra fits you well, then you're not the size on the tag either.

It's a good reminder to remeasure before starting a new project. I know I was really glad that I remeasured before starting my #GetawayWithALD capsule because turns out my measurements from last season were way out of date.

Also a good reminder to check your measuring tape before you measure yourself. Measuring tapes can also stretch out, so lay it against a cutting mat or yard stick to make sure it's still accurate.



If you measure with your existing bra on, you will only get an accurate measurement of what size that bra is. (Credit: Jan) Plus, if you're wearing your usual daytime bra and now you're measuring for a swimsuit or sports bra that you won't be wearing a bra with, those results wouldn't be useful.

It might be helpful to measure in a tank or a shelf bra though because it can help keep everything lined up. (a little bit of support)... and give you an indication of where to measure.

So band size first. You want to measure with your arms at your sides (I couldn't do that and take a photo, sorry!)

Pull the tape snug, but so that you can still breathe. This is your band or underbust size.

Now measure full bust across the fullest part of your chest. Be sure the back of the tape measure is in line with the fullest part of your bust as well.

Since taking off my bra, my full bust shrank by about 1.5". It's a wonderful bra....

Doing the math here for myself:

Sewing Cup Size = 46.5-42.5 =4" = D (determined above)

Now to calculate my Bra Size

I subtract my under bust (band) size from my full bust size and the same cup standards apply:

1″ = A cup

2″ = B cup

3″ = C cup

4″ = D cup

5″ = DD cup

6″ = DDD cup

...and so forth

So for me -

Bra Cup Size = 45-41= 4" = D

So I am one of those people that has the same sewing and real bra cup size, but that's kind of a fluke because of my favorite bra being super helpful!

Cup Size Siblings

I had never heard the term "Sister Size" before this year. At first I thought it was two pattern companies sharing a size chart. Nope! So I did some internet research and phoned some friends.

It's when two different bra sizes (combination of band and cup) share an actual cup size (not a letter - the actual dimensions of the foam cup). And PS, here at ALD we're going to call them "Cup Size Siblings" in order to avoid a gender specific term.

Bra cup size changes based on the band size. So a 32C is a smaller cup than a 36C.

I determined I'm a 41 D (PS no such thing as odd band sizes, so I'd have to choose to go up or down a size to buy a bra in store, usually down, so we'll call me a 40D).

Now what size cup do I buy? Well I and anyone else on the same line as me (my size siblings) would buy a size 26 cup from Amelia Lane Designs.

This is convenient for someone like me who is between band sizes. Let's say I had determined I was a 42 band instead of a 40 (since I'm a 41 and they only come in evens). Doing the math again, now my 45-42 difference is only 3" so a C. So I could either be a 40D or a 42C. Either way I order the 26 because those are sibling sizes!

Curious now about other size bras might have the same size cups as yours?

Let's check the chart!

For example, the cups on the 38A, 36B, 34C and 32D bras are all the same because they're in the same row on the chart. If you wear any of these sizes, you'd want to buy the size 12 cup from Amelia Lane Designs.

This way, if your size isn't on the abbreviated cup size chart (below) you can cross-reference the Sibling Size Chart (above).

But Why?

So I wrote this up because I saw questions in the Amelia Lane Designs Facebook Group about what size to buy. I couldn't answer them at the time, so I wanted to do some research and have an answer to give. This post is that answer!

So hopefully I've given some useful advice on what size cups to buy. But. We haven't discussed WHY to buy cups.

It might be obvious, but I'll toss it out anyway.

Cups provide some additional support in a garment. They help carve out room in the bodice to make the right shape and space for your chest.

There's soft foam cups (these) and you might've also seen molded cups at your local fabric store. Those are the hard ones that aren't flexible.

Cups can also provide really awesome "headlight" visibility protection. They're not just for sports bras or swimwear either. You can put them into summer tanks and dresses so you can have that layer of comfort to go bra-less.

They're also great for items that are strappy or backless and a regular bra would show. George and Ginger recently added them to the Mix It Up Dress during a Sew-Along for that reason. (You'll need to be a member of the G&G SAL group to view this link)

You can sew these cups in to hold them in place or you can put them in between two layers of fabric (or lining or power net) which makes them adjustable and often removable. A lot of people like to remove the cups before putting their clothes in the dryer, but it's not necessary.

The cups are shaped with a round side and two pointed sides. The round side goes up. (Your choice though, if they fit your shape better another way, by all means, customize your fit!).

Amelia Lane Designs does sell them in a pair but the left and right are not specific. So if you wanted to buy two different sizes (it's not uncommon to have two different cup sizes), you could make two custom fitting pairs.

My advice to figure out what sizes to order would be to measure your band size - this should remain the same. Then measure your full bust while suppressing the larger side until it's feeling equal to the smaller size. Calculate cup size for the smaller side. Then measure again, this time using your hand to exaggerate the smaller side until it's equal to the larger side. Calculate the difference to the band size again and you should have the cup size for the larger size. Now you could order two pairs, one in each size and made two custom fitting pairs.


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What are your favorite notions from ALD and what do you use them for? Tell us in the comments!

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Emily Igo Stevens
Emily Igo Stevens
Jun 05, 2019

Laura, thanks for such a detailed post on picking the right size!

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