We’ve learned that most commercial patterns are made for women with a B-cup (no more than 2.5″ difference between bust and high bust measurements). Today Beki from Artsy-Crafty Babe (and our Sew,Mama,Sew! board) provides resources and a great “how to” for Full Bust Alterations:

Generally, when you sew clothing for yourself, it is wise to choose the size that best matches your own measurements with those in the chart on the back of pattern. When you have a large bust, this isn’t always the best course. When you make a top based on your full bust size, you can easily end up with a tent! Just because you have big boobs doesn’t mean that you’re big everywhere else. You want to choose the pattern that best suits your frame. So, how do you do that?

Most commercial patterns are drafted for a B cup. Depending on the type of top you’re making, if your cup runneth over, you’ll need to do an alteration. This type of alteration is known as a Full Bust Alteration (or Adjustment), FBA for short. You may need to add a little or you may need to add a lot, but the good news is that it can be done.

The first step in determining what size to start with is to measure your upper bust. This is the area above your bust, around your body under your armpits. Use this measurement instead of your full bust measurement to determine your size. By using your upper bust measurement, you will be choosing a size that fits your frame, not your fluff. The top should fit nicely around your neckline and shoulders, avoiding the droopy shoulder seam, which is common when you make a size too large. Next, you need to know your full bust measurement. The difference between your upper bust and your full bust measurement is the amount that you need to add to your pattern.

There are many wonderful resources available for showing you the various methods of making a FBA. The alteration will vary depending on the style of top that you are making. I’ve included some links at the bottom along with some books that have been helpful to me.

To demonstrate a FBA on a princess seam, I’ll be making the Lotus Cami by Amy Butler. I’m using the method illustrated in Fit for Real People by Palmer Pletsch. Using my upper bust measurement, I’ve determined that I should make a size large, but I’ll need to add about 3″ to accommodate the girls. Because most pattern fronts are only half of the front, I’ll be adding around 1.5″ to my pattern. I’ve decided to add 1″ to my pattern piece because most patterns are drafted with added ease, which is the difference between your actual body measurement and the measurement of the finished garment, a little “breathing room” so to speak.

I always start out by tracing my pattern pieces. By doing this, I am not altering my original pattern.

On the side front piece, draw a line up from the bottom of the pattern along the stitching line to the full bust point, the angle the line towards the armhole at about 1/3″ of the armhole. Next, draw a line from about where a bust dart would be to the point of the angle.

Cut along the first line up to but not through the armhole. It is important to leave a hinge. Then, cut alone the side line up to but not though where the two lines meet. Next, spread the lines to the desired fullness (1″ in my case), making sure that the two sides of the first cut stay parallel.

Make a horizontal cut somewhere near the bottom of the patten in order to lengthen the right side of the pattern to meet with the left side.

Fill in the vertical gaps you just made, leaving the gap at the side open. Next. draw a line from the point of the side gap to the full bust point.

Cut along the line you just drew, then close up the side gap. This rotates the dart from the side to the full bust point. Fill in this gap.

On the front panel piece, make two horizontal lines, one at the full bust point, the other near the bottom of the pattern.

Cut along those lines, then spread open. The distance spread at the top cut should correspond to the distance spread at the rotated full bust dart (the part you just filled in on the side panel piece) and the distance spread at the bottom should be the same as the amount you spread near the bottom of the side panel.

Fill in the gaps. Your front pieces are now ready to be used.

Here is my completed Lotus Cami. Judging from the photo, I probably should have added a little bust more to the bust area. It is important to note that just because you make adjustments doesn’t mean that it will work out the first time! This is why I make my first version out of inexpensive fabric. I would have been really disappointed if I had made this top out of my good fabric.

By making this version I learned a lot about how this pattern goes together. I now know that it is crucial to line up the upper bodice properly. I had a little trouble with this on the right side and it shows. I also had a trouble with the facings. (Never mind that I bound my right armhole on the wrong side – we all make mistakes!!) This was my “muslin,” so it’s okay to make mistakes. I do like this top and plan to make it again.

  • Books in my own collection:
    Fast Fit, Sandra Betzina
    Real Fit for Real People, Palmer Pletsch
    Fitting Finesse, Nancy Zieman