FBA

In the Sewing Matrix the term FBA is not what regular Earth people think it is. It’s not a kind of a fashion police either. It stands for Full Bust Adjustment. It’s a pattern manipulation technique that allows you to enlarge the cup size.

If you met me, you might have noticed I’m unlikely to need full bust adjustment no matter the pattern. Good for me since it makes things way easier. That’s the thing; most of sewing patterns are made for the B cup. For those of you cursed with cups bigger than B, this technique will prove very useful, typically if the garment feels awkward around the chest or the fabric pulls at the front and is simply too tight in that area.

You can use this technique regardless of the cup size really, I still make FBA in some patterns to add more fullness and – let’s not be afraid to say it out loud – cheat a little and shape a more feminine silhouette. Here’s how to do it!

Find those numbers

Always start with measurements. To determine your cup size measure upper bust first. Then measure your full bust. The difference between those two indicates your cup size.

If the difference equals 1in you have the A cup, 2in is the B cup, 3in is the C cup, and so on.

Let’s assume that you’re size D. The pattern is for size B. It means that you have to add 2in more around the bust (B=2in; D=4in → 2in difference between B and D). Now that you know how much you need to add, the question becomes what size should you enlarge?

This is important since the pattern is designed for the B cup. So if your bust measurement is 38in, subtract those additional 2in (the difference between B and D) when choosing the size. In this case you’d choose 36in, taking under consideration your true hip and waist measurements as you would usually do. In other words, all else being equal, your bust would measure 36in with the B cup.

Draw, cut, shift

Draw:

·      a straight line through the middle of the bust dart toward the center of the pattern (blue line);

·      a line through the middle of the vertical dart toward the center of the pattern (red line). The intersection of these two lines indicates the bust apex;

·      a line from the bust apex toward the armhole, just above the most curvy part (green line);

·      a horizontal line just above the vertical dart (pink line).

Cut:

·      along the red line from the pattern’s edge and further along the green line. You want to leave a tiny hair of paper at the armhole so those two parts are easy to shift but aren’t entirely separated;

·      along the blue line from the pattern’s edge toward the bust apex. Again, don’t separate it entirely.

Now, in the example we agreed you need to enlarge that area by 2in. The front pattern piece is actually ½ of the whole front (if for instance it’s cut on fold). That’s why we need to divide 2in by two as well. We get 1in. Take a piece of paper, just to cover the cut area. Draw two vertical lines on it 1in apart. 

Shift:

·      align the red line on the paper along the drawn line. Tape it only above the dart for now. You will shift the part under the pink line later;

·      tape the other red line along the other drawn line;

·      secure the green line with tape as well;

·      cut along the pink line and move the bottom part so it’s the right length again. Tape it.

Here is how it looks in motion:

You are almost done! Mark the new apex point at the same height as the previous one. Just move it left to the center of the new vertical dart.
Draw the new darts starting 1.5in from the apex.