Designing a graded pattern for an “FBA” or Full Bust Adjustment – Warning: This is Technical – Part 1

I recently created a pattern called the Rachel Tank, with 5 bust size options. It was a challenge to determine how to break down the sizes. I wanted to create a versatile pattern, but really didn’t want to have to create a different pattern piece for every bust size known to man.

I chose this simple design to help me establish my grading for bust sizes in RTW styles. I know grading extensively for bra making and for basic patterns, but I never tried adjusting a pattern for a full bust. This series is on how I altered a basic tank with a “FBA” or full bust adjustment. I don’t go into the nitty gritty of making changes, but this series tackles how I created my grade rules for the FBA on a RTW garment style.

I first took a basic tank from my Porcelynne collection from years past. It is a simple tank I made thousands of times over the years. It was great for me when I was on the thinner side. I might have been a DD when I was a size 10/12 in the past.

I am now a I/J cup and a size 18, although I am slowly losing weight. I laughably tried on one of my tanks from my younger days and thought – well, this won’t do. I need to create something for “real” women, aka myself.

I spent several hours redesigning my basic Porcelynne tank to include a dart – which makes it shaped better on the body. I also removed some of the fitted-ness of the top. I figure it is always easier to remove, than add, once it is sewn together. For someone who wants a more fitted tank, the individual can take it in on their own.

I had already spent hours (but closer to days) developing the size chart of my Christina Sports Bra. I planned this to be the base of all my sizing. I will try to walk you through my grading madness.

I have a spreadsheet with multiple tabs going. Some accounting for stretch on a garment and some for non-stretch. I probably won’t share all of it, as it was a lot of work on my part and honestly I am always adding to it when working on a new garment. (This is a foreshadowing that I will be writing a book on grading- but not today!)

Step 1: The Size Chart

When making the grade, I first needed to create my size chart, aka my grade rules. I used my existing sizing from the Christina Sports Bra. This is only for part of my size chart – 28 through 40 Bands (the rest of the chart can be seen on the Christina Sport Bra product listing). The cup amounts are the full bust measurements.

I took this size chart and accommodated it for letter sizes, meaning small, medium, large, etc. I took the basic size measurements for the B cup for the A/B Cup sizes of each letter size. Letter sizes generally cover a range of number sizes. For example, a small covers dress sizes 2 and 4.

Not everyone has the same chart. Mine may not be appropriate for you to use. Mine is for my customer. I have already trained my customer with my previous patterns (California Dreaming and Christina Sports Bra). My existing customer knows how my patterns fit, so this size chart reinforces my existing fit.

I added the corresponding dress sizes, my sports bra band sizes for reference, waist, hip and my basic bust size of A/B. As you can see by just looking at the XS, the A/B cup size is my B cup for the 28.

Things got more complicated for the rest of the sizes. I had to make a call on how my sizes were created. I initially took the smallest A measurement for the smaller size and B measurement for the larger band size. For the small, that would be 31-34, which is a 4 inch range.

Letter sizes are traditionally a 4″ change in circumference from size to size (not including any stretch adjustments). To me the 4″ change for the bust size was too big of a change for each cup size.  

I opted to make my bust size range only 3 inches instead of 4 for the A/B, but only 2″ for all other cup sizes. I played around a bit with my numbers and this is the chart I came up with. 

My bust sizes don’t necessarily equate to the actual bust sizes from the sports bra size chart, but they are close.

Step 2: Measurements for Patterns

The size chart was the hardest part of all of this, but I can use this size chart for all my future patterns. It is important you have a sound size chart prior to developing any patterns.

The second step was to determine what measurements I was basing my patterns on for each size. You can’t have a range at this point, only a singular number for each point. I started with my waist and hip measurements since those were the simplest to create.

If you notice, the waist measurement I listed here is larger than the largest size in each range. This accounts for 2″ of ease in the garment. Remember, I have not adjusted the charts for stretch, so this chart is still being built for normal ready to wear. Some pattern companies may use the middle of the range and some may use the lower end of the range. These decisions are done by the designer and no choice is considered wrong. I prefer my patterns to be on the generous side, than “smaller than expected.”

In this chart I write in the full amount with ease, then break the amount into 4 since most drafting is done on one quarter of the body. I also list how much my grade is between each quarter amount. This shows my growth per size, or my grade per size.

Am I losing anyone yet?

I will stop here for the day. The bust grades are more complicated, so I’ll let this sink in for a day or two. Tell me what you think I might do for the bust grades. I’ll include the result in Part 2 of this post.

If you ever wonder why its so expensive to hire pattern makers or why pattern makers always ask for a defined size chart, hopefully this will help open your eyes to why we ask for it.

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