How to determine what size your bra was drafted for

How would you like to know what size your bra was actually drafted for?

Since there are so many different ways people measure for fitting bras, I thought I’d try to shed some light on why some people measure some ways and why some people measure other ways.

The first thing to cover is how people measure. I have encountered 4 different measuring techniques, but the one thing that is common among all of them is that you subtract your band number from your full bust measurement to determine your cup size. For each inch difference, there is a cup size.

The differences come into play based on how to come up with the band size. The most common measuring technique is to take your underbust measurement and add 4″ or 5″. Specialty shops generally take your underbust measurement and add 2″ or 3″. International measuring either take the underbust measurement as your band size or your chest (above the breast) measurement as your band size.

So, which one is correct? The short, but frustrating answer is, “All of them.” Each one of them were developed based on how a pattern was drafted, but how do you know what measurements they were drafted for?

The next short, but frustrating answer for that is, “you don’t know.” I am on a quest to find out what sizes these bras were drafted for.

I started with a paper with a line on the far left. I also did a lower horizontal line, but that was unnecessary (skip that if you are doing this yourself). I pinned the center of each bra and lined up the center front to the left line.

I first marked the position of the wire with it just sitting. I then straightened the band, which moved the wire and marked the same point on the bra with the wire sprung. That was done for a later post, but thought I’d explain what I did.

With the side of the band straightened out, I marked where the side seam was on both the top and bottom of the bra, then marked where the back ends before the hook & eye.

Each one of these is a different manufacturer, let’s determine what size these were actually drafted for. I did a video as well (link is at the bottom) but it might be a little technical and boring, except for the parts where the cat tried to get some love while I was filming.

I repeated this for 4 different bras. Notice that the angles of the side seam are very different, meaning that the body proportions these were drafted for, were very different as well.

I marked a horizontal line from the center front to the top and bottom of the side seam and indicated the measurements.

I then drew in the back lines from the side seam to the back and measured those as well.

Once all those measurements were recorded, I then tested the back for stretch. Now, the one thing I had taught in my previous books is to take into account the stretch of the back fabric, but in actuality, you need to know the stretch of the elastic, which is generally snugger than the fabric. In fact, you can really use any stretch fabric you want for the back, IF you have the right elastics to stabilize the fabric.

Ok, so to test the stretch, I tested the elastic itself. I marked in pins at 0 and 5″. I then lined it up to a vertical and horizontal line and stretched the elastic to a comfortable stretch. This stretch was not the full amount the elastic stretches it, its the amount it stretches before you hit resistance. The point beyond resistance can be very uncomfortable.

I then referred to my stretch ratio chart and reverse engineered the back lengths. I took the amount of the back (and really only the underbust measurement matters) and divided it by the stretch ratio to determine what the measurement it should fit on a person.

Ok, now I’m jumping around a bit. Lets first determine the difference from chest to underbust. Subtract the underbust from the chest amount for the front and multiply by 4. That is the difference for the entire bra between the chest and underbust measurements.

To determine the actual underbust measurement this was drafted for, add the front band, the new underbust measurement on the back plus 1″ for the hook & eye. Then multiply by 2. Voila. That is the underbust measurement this was drafted for.

Then add the chest difference to determine what chest measurement this was drafted for. Voila. Now you know.

One thing to note is that bras are designed for generally the smaller measurements in a range, so a comfortable fit would be for those two measurements plus up to 1″, maybe 1 1/2″ max.

The next question I approach is which measuring guidelines match each of these bras:

Black Bra: 38C by Maddie & Coco (cheap bra from Bealls)
Measurements drafted for: Underbust 30″, Chest 35 1/2″
Measuring technique: Chest +2/3 or Underbust +8
5 1/2″ Difference from Chest to Under Bust

White Bra: 38B Body Frosting (cheap imported brand)
Measurements drafted for: Underbust 31″, Chest 33 1/4″
Measuring technique: Chest +4/5 or Underbust +7
2″ Difference from Chest to Under Bust (approximation)

Nude Bra: 40C Wacoal
Measurements drafted for: Underbust 32 3/8″, Chest 35 3/4″
Measuring technique: Chest +4/5 or Under bust +7/8
3 1/2″ Difference from Chest to Under Bust (approximation)

Brown Bra: 42C by Pink (Victoria Secret),
Measurements drafted for: Under bust 36 5/8″, Chest 41 3/8″
Measuring technique: Chest measurement
5″ Difference from Chest to Under Bust (approximation)

Ok, I was not expecting those measurements for those sizes. Now I’m curious what the manufacturers recommends.

Just checked Wacoal. They recommend under +3/4, but no mention of the chest. As far as I can tell, this bra was possible drafted based on the fabric stretch and not the elastic stretch. The fabric stretched far more than the elastic did. Wacoal always fit me best, but the bands were often a little tight for me based on their recommendations.

I also checked Victoria Secret and at least their measurements match their recommendations. The other two brands are cheap and likely made in some factory with little to no reference of sizing.

I can see why so many people wear the wrong size bras. It isn’t really an issue with the measuring, it’s an issue with the drafting. Every part of the bra needs to be accounted for, in every aspect of the draft. (A wire discussion will be a later post.)

The elastics play an integral part to the way a bra fits and if the bra is only being drafted based on the fabric and the elastic isn’t incorporated into it, the bras can fit drastically different based on which notions are used.

Why don’t you try this yourself and share with me what you discover about your favorite brand. How does their measuring size up to the actual bras you have?

Here is the full video:



This is all part of the research I did for the third edition of my bra drafting book. Now, I know that some of you are wondering why I would write a third edition in 7 years. Not sure if you knew this but the big textbook publishers do a new edition every 2 years, so I’m not far off.

BUT, I do not plan to write another edition of this book, EVER! When I wrote my first book, I researched all the available information out there and tested and tested. I developed my own drafting techniques and they worked. I still say that they worked, even though I am writing the 3rd edition.

What changed is me. My body changed after having a child so I began to look at drafting a whole lot differently. The second edition also included instructions on how to draft in CAD. The second edition I am also proud of. I have found a few typos and wording that could have used a little more editing, but the second edition showed different ways to do the same thing.

Over the past 3 years I have gotten involved with a few bra making groups on Facebook. It has opened my eyes to even more issues that ALL bra drafting neglected to address.

I decided last year that I was going to do more scientific and mathematical research to thoroughly understand the underlying issues and how to fix them by drafting a truly custom fit. That is what I have been working on.

I created a calculation to determine the horizontal measurement for a cup draft based on the wire size, under bust, full bust and chest measurements. I then was able to create a calculation to determine the vertical measurement of the cup incorporating one additional measurement, the chest height. With these new calculations, I have been able to get to a more accurate draft on the first try.

Those are just some of the reasons for the third edition. I’ll share some more in my next post.

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