November 19, 2020

How to Do a Small Bust Adjustment (SBA) on a Princess Seamed Bodice

If your bust is smaller than a B cup, or the difference between your high and full bust measurement is less than 2″, then you may need to do a small bust adjustment. Here’s how to do an SBA on a princess seam bodice.

In this tutorial, we’re showing how to do a small bust adjustment on a pattern that has princess seams – it’s the same technique for armhole or shoulder princess seams. If haven’t done an SBA before, check out this post which will help you work out if you need to do one, and if so, how much you need to adjust by.

Preparing for an SBA

Here’s what you need on hand for doing your SBA: your front bodice pattern, some tracing paper (we like Swedish tracing paper, but anything that you can see through will do), a pen or pencil, a ruler, scissors, and some tape. It helps to be working on a cutting mat or a surface that you can tape things down onto temporarily—you’ll see why pretty soon.

We always recommend tracing your pattern piece before starting to cut into it. This is so that you can refer to the original piece later on if needed—once you cut into the real thing, it’s hard to go back.

How to do a princess seamed SBA

  1. We’re going to start with the side princess bodice panel. First, draw on the seam allowance around the armscye and front sides as shown. Then you need to draw three lines: the first one is line A, and it goes horizontally across the piece to the bust apex (that’s where the curve sticks out the most). Line B goes from the bust apex down to the seam allowance at the bottom. Line C goes from the apex up to the seam allowance at the top.

2. Draw another line parallel to B, which is the width you need to remove in your SBA. Now, cut up line B and C, stopping at the seam allowance. Then make a little hinge but cutting into the allowance on the other side. Then, cut down line A, starting at the side seam and ending with a small hinge.

3. Swing the bottom piece over and up, so that the right hand side piece (where the princess seam is) meets the dotted line. As you do this, the upper part will have to also swing down and to the side – and you may end up with a little bit peeking out beyond the princess seam.


4. The bottom is now uneven. Draw a horizontal line across the right hand side piece, cut across it, and slide the bottom piece up until the hem is level again. Measure the amount of overlap when you slide that piece up.

5. Trace the pattern piece. Ignore the little bit poking out past the princess seam! And make a marking where you overlapped the small piece at the bottom.

6. Now we have to alter the center front piece to match. Measure up from the bottom of the side piece to the marking you made to indicate the overlap. Now measure up the same distance from the bottom of the center piece, and draw a horizontal line across the piece.

7. Cut across this line, and then slide the bottom piece up by the same distance as you did on the overlap on the side piece.

And that’s it! You now have a new princess seam that’s narrower and shorter to suit your smaller bust.


Want to learn more about fitting clothes to your body?

Check out our Fitting for Curves: Pattern Adjustments for the Upper Body online workshop.

2 thoughts on “How to Do a Small Bust Adjustment (SBA) on a Princess Seamed Bodice

  1. Brenda Marks says:

    Thank you!

  2. Judith says:

    Do you have to shorten the back piece also. The side seam of the bodice part is shorter because of the SBA? The harrison shirt has a front middle piece and front side piece. Which part do I use for a SBA?

Let me know what you think!