First, you will need to determine whether you need a bust adjustment, and if so, how much. To do this, it’s very helpful to make a muslin, since the adjustment amount can vary depending on the silhouette of the garment, your body type, and your preferred ease.
Bust adjustments are not always necessary! Some patterns with a loose fit will work for a wide variety of body types without any need for modification. Depending on your personal style, you may choose to just size up or down.
1/ On the front bodice, mark the bust apex (the point that corresponds to the tip of the bust). Draw a vertical line (parallel to the grain) from the bust apex to the hem. Draw a horizontal line (perpendicular to the grain) from the vertical line you just drew towards the center front. Finally, draw a line from the bust apex to the center of the shoulder gathers.
2/ Slash the bodice from the vertical line through the apex and towards the shoulder. Pivot the side seam piece at the shoulder towards the left until the gap in the bust apex is equal to the bust adjustment value.
3. Pivot the side seam piece at the bust apex towards the right until the bottom vertical lines are parallel. Note that this will create a gap at the shoulder.
4/ Slash the horizontal line. Slide the lower piece down until the bottom edges are in alignment.
5/ Tape together and secure the pieces you just adjusted. Take a new sheet of pattern paper and trace the edges of the bodice. Draw the gather line again.
1/ On the front bodice, mark the bust apex (the point that corresponds to the tip of the bust). Draw a vertical line (parallel to the grain) from the bust apex to the hem. Draw a horizontal line (perpendicular to the grain) from the vertical line you just drew towards the center front. Finally, draw a line from the bust apex to the middle of the shoulder seam.
2/ Slash the bodice from the vertical line through the apex and towards the shoulder. Pivot the side seam piece at the shoulder towards the right until the overlap at the bust apex is equal to the bust adjustment value.
3. Pivot the side seam piece at the bust apex towards the left until the bottom vertical lines are parallel. Note that this will create an overlap at the shoulder.
4/ Slash the horizontal line. Slide the lower piece up until the bottom edges are in alignment.
5/ Tape together and secure the pieces you just adjusted. Take a new sheet of pattern paper and trace the edges of the bodice. Draw the gather line again.