To get the best possible fit on your handmade garment, you often have to make some adjustments to the pattern: lengthen or shorten some seams, add a little width to the hips, take the waist seam in…
One of the most feared, but most efficient, adjustments is the full bust adjustment, “FBA,” along with its twin, the small bust adjustment. Just looking at the diagrams for these fixes might give you a headache. Truth be told, that’s what I thought too before looking at it for real. That’s when I realized that these charts could make sense and weren’t so terrifying after all!
Follow along with this a step-by-step photo tutorial to learn how to make a full bust adjustment on a princess seam, so you too can conquer the adjustment beast!
What is a full bust adjustment?
A full bust adjustment is the most common way to make a bodice sewing pattern larger at the bust. By cutting the pattern pieces and slightly moving them, you can easily add inches to the finished garment.
Before you begin…
If you haven’t already, take your measurements. For this adjustment, the two most essential measurements are your bust and your waist.
Then, it’s a good idea to make a muslin of the bodice for your pattern to know how much you need to increase the bust area. If your bust size is one or two sizes higher than your waist size, you might need a FBA. Another good indication is to look for the cup size on the pattern, as most patterns are designed for a B or C cup.
For a pattern similar to one in the picture above, you would choose your size according to your waist measurements. Let’s say that, for example, your waist is 29″ (size 40) and your bust is 38″ (size 42). The bust measurement for size 40 is 36,” so there is a 2″ difference. You’ll cut the pattern in size 40 and add 1″ (at each bust seam) to make the full bust adjustment — without ever increasing the waistline or the neckline.
Cut out your pattern bodice front and side-front pieces. Draw the seam allowances and all the marks (notches, grainline, etc.).
On the bodice side-front piece, draw 3 lines:
- A straight line from the waistline to the fullest part of the bust.
- A diagonal line from 1/3 of the way up the armhole (remember that the armhole is made of the the front and side-front bodice pieces) to the fullest part of the bust.
- A diagonal line from the fullest part of the bust toward the side seam allowance, like a dart.
Place your pattern piece over tracing paper. Cut lines 1 and 2, leaving the armhole seam allowance intact.
Carefully cut the seam allowance, but make sure it’s still attached (see above).
Cut line 3, stoping just before you reach the fullest part of the bust. You want the the three pieces to be connected but individually movable.
Tape the princess seam to a piece of paper and pivot the pattern along lines 1, 2 and 3, so that the opening at line 1 measures 1″ (or however large your increase needs to be). Make sure the increase is even all the way down line 1. Tape the pattern in place on the paper.
As you can see above, the waistline (bottom edge) on the princess seam piece is not even with the waistline on the side front piece. Draw a line parallel to the waistline on the princess seam part.
Cut along the line. Move the cut piece down until it aligns with the waistline of the side front piece. Make sure it is also aligned with the rightmost edge of the princess seam piece. Tape in place.
With all the pieces taped in place, cut roughly around the new pattern piece.
Draw a line to extend line 3 all the way through princess seam.
Cut along line 3 (the horizontal line) from the outer edge until you reach the fullest part of the bust (line 1).
Pivot the “dart” closed, so that the bottom side front piece meets the armhole piece. Tape in place.
Cut the line 3 from the outside edge of the princess seam to the fullest part of the bust, but don’t cut all the way through. Spread the “dart” open until the bottom edge aligns with the bottom edge of the side front piece. Place a piece of paper under the spread “dart” and tape in place.
Now is a good time to trim away the excess pattern paper around the paper pattern piece.s
To keep the waistline the original width, we need to remove the width we added to the bust (1″ in this case). Draw a new side seam starting from the rightmost edge of line 3 and ending 1″ from the waistline edge.
Next, you’ll need to add the increases you made to the side front piece to the front piece. Trace 2 lines at the same level you made the two increases on the princess seam pieces. Cut along these lines.
Measure how much you added at each increase on the side-front piece, then add the same measurement to the front piece at the corresponding places. For the bust, measure the seam allowance line, not the cutting line.
There you go: Your new pattern pieces are complete! We have “magically” increased the bust area without touching to the waistline, armhole or neckline.
Confidently Adjust Any Pattern!
Embrace your shape! Adjust any pattern to fit and flatter your figure with step-by-step guidance from instructor Jenny Rushmore.
Editor’s Note: This post was originally published in July 2014 and was updated in March 2018.