Sometimes patterns are designed with more fullness in the bust than you need. When the pattern uses princess seams, you can't just adjust the side seams to get a better-fitting bust. You'll need to learn how to do a small bust adjustment (SBA) for princess seams — and I'm here to help!
(If you're working with a darted bodice, check out this post on doing a small bust adjustment on darted seams.)
LET'S LOOK AT THE FRONT PATTERN PIECES FOR A TYPICAL PRINCESS SEAM BODICE PATTERN.
The center front piece is cut on the fold, and the side front piece is attached to the center front piece with a seam that runs vertically from the waist, over the bust up to the armhole.
The fullness to accommodate the bust is between the notches, which are on both pattern pieces. The curve and length of the side front is better suited to a full bust than a smaller bust.
HERE'S HOW TO ADJUST A STANDARD PRINCESS-SEAM BODICE FOR A SMALLER BUST.
STEP 1: MEASURE THE PATTERN
Measure the stitching line of the side front pattern piece to find the distance between the two notches. This step takes a little practice, but is a useful skill to have.
Make sure you're measuring 5/8" from the edge. It helps to draw in your seam allowance so you can measure on the right spot.
Measure starting ta the center of each notch. I like to draw a line between the notch and the stitching line for accuracy.
I recommend turning the tape measure on its side to measure this curved line.
If your tape measure is too stiff or you have trouble with this measurement, you can also lay piece of string along the stitching line, cut the length and then measure the string. Save the piece of string to use in a later step.
In this example the distance between the notches measures 4¾".
STEP 2: REDUCE THE SIDE FRONT PATTERN PIECE
Reduce the side front pattern piece by drawing a new stitching line inside that removes some of the curve and fullness over the bust apex.
I like to determine how much circumference I want to take away from the bust then measure in that amount. For this example, I reduced the front across the bust by 1" total.
On the side front pattern piece, I marked ½" in from the existing line, right at the fullest point. Then I used a curved ruler to draw in a new stitching line between the notches.
Measure the new stitching line using the same method as before, or place the piece of string and measure the new length. In this example the new stitching line measures 4½" which is not a big difference in length but has reduced the total bust circumference by 1".
STEP 3: SHORTEN THE CENTER FRONT PIECE
Once the side front piece has been adjusted, the center front piece will be too long, so it also needs an adjustment.
Here's where you'll need those before and after measurements of the distance between the notches. In my example, the difference is ¼", so the center front piece also needs to be shortened by a ¼".
Create a fold between the notches that meets that measurement (you can see mine drawn in pencil above). Tape the fold closed. Smooth out the stitching line and cutting lines as needed — though a ¼" or ½" should not make much of a difference in the edge on the pattern.
STEP 4: REDRAW PATTERN EDGES
On the side front piece, draw in a new cutting line, using your pattern's indicated seam allowance. Here it is 5/8". Cut away the excess.
And that's it! Your pattern is adjusted to your own shape without excess fabric over the bust.
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