In this post we will cover how to do a Small Bust Adjustment for the Myrtle. You’ll find this helpful if your pattern cup size is smaller than a B cup for XS-XL and D cup for 2X and 3X.
Pattern Cup Size
When sewing, your cup size is determined by the difference between your high bust (also called upper bust) and full bust measurements. It may or may not correlate with your bra cup size, so you should not use your bra size for reference.
Your high bust measurement is the distance around your chest above your bust, under your armpits.
Your full bust measurement is across the fullest point of your bust.
A difference of 1” is an A cup, 2” is a B cup, 3” is a C cup, etc.
Some fitting problems that may indicate you need a SBA:
- When you choose a size based on your full bust measurement, the finished garment is too tight in the shoulders/armscyes/upper back.
- When a garment fits you in the shoulders and across the upper back, across the bust it is baggy, gaping and too loose.
Most sewing patterns are drafted for a B cup, but Colette patterns (XS-XL) are drafted for a C cup. That means they assume a 3” difference between your upper bust and full bust. If you have a difference of 2” or less, then you are a SBA candidate.
Colette’s plus size patterns (2X and 3X) are drafted using a different fit model with DD cups, meaning they assume a difference of 5″. So if you have a difference of 4″ or less in those two sizes, you are a FBA candidate.
Choose a size and SBA amount
For this post, I’ll be working with measurements of a 32” high bust and 34” full bust to illustrate. Just substitute your own measurements in as you follow along.
To choose our size, we are going to select based on our high bust measurement so that it fits in the shoulders. Take your high bust measurement and add 3” for the assumed C cup. This is your imaginary full bust measurement that you will use to pick your size. So, if my high bust is 32”, my imaginary bust measurement is 35”, so I will choose a size Small.
Now we have to figure out the difference between the imaginary and real full bust measurements. If my full bust is 34”, that means I need to subtract a total of 1” across the bust. Because we are only going to be doing the SBA on one side of the bodice – the front bodice is cut on the fold – I need to subtract half that amount, since it will be doubled when the fabric is cut. So I will subtract 1/2” when I do the SBA. Whatever your measurement is, we’ll call it [X].
Do the SBA
Myrtle’s front bodice is unique in that it’s a mirror image that will be folded in half to create a self lining. For the SBA, we are only going to work with half, then retrace it when we are finished to recreate the fold line.
Trace off the front bodice in your size, using the dotted shoulder fold line as the top edge of the pattern piece.
Hold the pattern piece over your body and mark your bust point, which is the fullest part of your bust. Use the side seam and armscye to make sure it’s properly positioned.
Now we are going to draw some lines. Draw a line from the bust point down to the bottom, parallel to the center front edge. This will be line A.
Draw a line from the bust point out to the armscye, about a third of the way up. This will be line B.
Draw a line from the bust point out to the side seam, about where there would be a bust dart (1-2″ from the top of the side seam). This will be line C.
Draw a line perpendicular to line A, right under the notch on the side seam. This will be line D.
(Note: You can also use the lengthen/shorten line as line D.)
Lastly, draw a line along the stitching line at the armscye, across line B. Since our seam allowance is 3/8”, this means 3/8” in from the edge. Draw several short little lines to make it an accurate curve.
Ok now we are ready to slash! From the bottom, cut up along A, then onto B, all the way up to but not through the stitching line.
From the armscye edge, cut to but not through the stitching line. The goal is to leave a little bit of paper intact so that you have a hinge.
From the side seam, cut along line C to but not through the bust point, creating another hinge.
Now is the time to remember your SBA amount, [X]. Draw a line to the right of line A, parallel to the cut edge, [X] distance away. Mine is 1/2”.
Use the hinges to overlap the left side of the pattern piece and position the cut edge along the line. Tape in place above line D.
Now we must account for the length we’ve taken away and even up the bottom edge. Cut the right side of line D, and reposition so that it lines up with and is parallel to the left side of line D. Tape in place.
Lastly, we will readjust the waistline. We want to keep our decreased width across the bust, but we want our bodice waist to still match our skirt waist. Cut along the left side of line D and slide the bottom piece over to the left so that the lower half of the bodice is no longer overlapping. Tape.
Redraw the side seam edge with a curved ruler, blending from below the bust to the bottom.
Use a ruler to neaten up the armscye and trim all paper.
We have decreased the fullness across the bust, but we also shortened the length of our side seam. Since we’re working with a knit, we have a couple different options for how to deal with this.
- Ease it in. You should be able to ease the back side seam into the front as you sew. If you feel like the difference is too great, you can cut a piece of clear elastic the length of the front side seam and baste it to the back side seam while stretching it, then sew the edges together. Check out this post on The Coletterie for more help with clear elastic.
Rotate the bust reduction into the cowl (detailed below). This will take a bit more patternmaking work, but it will move the side seam change into the cowl. This will return the side seam to its original length without changing the amount of fullness, but it will slightly change the scale and size of the cowl.
Rotating the SBA into the cowl
Draw a new line from the shoulder point down to the bust point.
Slash along this line up to the bust point to create a hinge. (You may also have to cut through a layer of paper that is now under line C.)
Rotate the shoulder on the hinge to return line C to its original place. Tape.
Draw a new top edge from the shoulder to center front, perpendicular to center front.
If you’re working with a woven, follow the main instructions. Then you can either rotate the SBA into the cowl as detailed above, or you reduce the length of the back side seam to match the front.
Redraw bodice piece
Once you are completely finished doing any adjustments to your pattern piece, retrace it on a new piece of paper, then flip it over the top edge and trace again to get your entire front bodice piece. Transfer any fold edges, dots and other labels.
If you have any questions, please ask away in the comments!