Have you found the perfect pattern but don't quite fill out the bust? No problem! The SBA (small bust adjustment) is great pattern adjustment to have in your repertoire.
While most women's sewing patterns are designed for a B cup, we all know that everyone has a unique shape. One woman's B cup might be much too roomy on some. This adjustment can make the bust on a bodice front with a horizontal bust dart smaller and more fitted.
How to do a small bust adjustment
Step 1: Identify the bust apex on the pattern piece
Some patterns have the apex marked (as shown with the circle), while on other patterns you will need to identify the bust apex. The bust dart generally points to the apex on the pattern, which is typically about 1" to 2" from the end of the dart point. This may or may not match your apex, and you might have to adjust the location on the pattern.
Step 2: Draw the lines
You'll need to draw four simple lines on your pattern piece:
- First, draw a line through the center of the bust dart to the apex.
- Next, draw a line from the apex down to the bottom of the bodice, parallel to the center front.
- The third line is draw from the apex up to the armhole, about 1/3 of the way up from the bottom of the armhole.
- Add a fourth line, horizontally near the bottom of the center front, connecting the vertical line with the front edge. This will be used to reduce the length of the center front section of the pattern.
A small bust adjustment both reduces the circumference around the bust and the length of the front of the pattern piece. A larger bust has more length from shoulder to waist, and a smaller bust has less length from shoulder to waist.
Step 3: Cut along the lines
Cut along the lines as shown above, leaving the pattern paper attached by a small hinge at the armhole and at the end of the line that's through the dart. It helps to put small pieces of tape over the pattern paper before cutting to reinforce those spots. Don't panic if you cut all the way through, but note the idea of these hinges, which helps you to shift the pieces in relation to each other.
By the way... the photo above also illustrates how you would do a FBA ( full bust adjustment ). If you were making the bust larger, you would fill in the spaces between the cut pieces with paper, adding both length and width over the bust. The SBA basically does this maneuver in reverse, as you will be reducing both the length and width over the bust.
Step 4: Shift the pattern pieces
Move the side section toward the center, overlapping as shown. Keep the side piece parallel to the center front piece so that you are reducing the circumference by an equal amount of length. The bust dart will become smaller as you shift the side toward the front and a smaller bust needs less length so the front becomes shorter.
Move the remaining small square piece upward to make the bottom of the pattern piece even. You will now be sewing a smaller dart; however, you have not changed the length of the side seam, so it will still match up to the back bodice piece.
Wondering how much to take out? Moving the side over ½" reduces the front bodice by a total of 1". The difference between cup sizes is roughly 1". I suggest you do a tissue fitting of the pattern prior to cutting it up to see how much to take out.
If you are sewing for girls or anyone with a small bust who doesn't need a dart, or prefers the look without a dart, it's possible to remove it entirely. While it's a bit unorthodox, there is no rule that says you can't pin the dart out and flatten the pattern piece back into 2-dimensionality. Be sure to maintain the straight edge at the center front of your pattern piece.
Do you have any tips or tricks for a SBA? We'd love to hear about them!
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