Sewing a Full Bust Adjustment (FBA)
Continuing with our Bust Adjustment series! Today we will walk through every step of doing a full bust adjustment (FBA) on a pattern piece with no dart. This is often on knit fabric but could be a woven pattern without darts as well.
If you have not already, take a look at the Bust Adjustment 101 post, for all the details on when to do the bust adjustment, and how to know what adjustment needs to be made. This will help you calculate exactly how much you need to add to the pattern piece in your FBA. Need a Small Bust Adjustment (SBA) instead? Check out how to do that alteration here!
A full bust adjustment is done when the full bust to upper bust difference is LARGER than the pattern is drafted for. By doing the FBA, you are adding more fabric to the bust area, without making the rest of the bodice larger. This gives a perfect custom fit for your individual shape!
Let’s Get Started!
Preparing the Pattern piece
You will need to start with TWO of your pattern pieces. The original for you to refer back to later in the process, and a tracing that you can cut up.
Begin by marking the apex point on the pattern piece. Some patterns will include this marking. If yours doesn’t, or for a custom fit, hold the pattern piece to your body and mark the point of your apex of the fullest part of the bust. Do this while wearing the undergarments you plan to wear under the finished garment.
Next, draw the lines that will be used for cutting the pattern. The first line runs from the apex point straight down to the hem. The second runs from the apex point horizontally across to the side seam. The third goes from the apex point to about 1/3 of the way up the armscye from the armpit point.
Begin cutting the pattern piece starting at the hem, cutting up the first line, through the apex point, and continuing through the line that runs to the armscye. STOP at the armscye edge, do not cut through this point (shown in red in the second drawing). This will be a hinge.
Then, cut from the side seam on the line that runs horizontally to the apex. STOP when you get to the red point at the apex. This will be the second hinge.
The following drawing shows what it should look like when you have finished cutting.
You should now be able to gently rotate the hinged pieces as shown above.
Starting the FBA
If it is helpful, label the three pieces of the bodice as A, B, and C as shown above.
Determine the amount you need to adjust the pattern piece. In this example, I am adjusting the pattern piece by 1/2″. (Unsure how much to adjust? Refer back to Bust Adjustments 101.)
Keeping B and C together, rotate away from A on the armscye hinge. Rotate until the apex point of B/C is the distance away from A that you need to adjust. I am adjusting by +1/2″, so I rotated until the apex point is 1/2″ away from A.
Keep B in place, leaving C free to move.
Rotate C on the apex hinge, until the vertical line of C is parallel to A, and there is the 1/2″ gap between the two.
Next, you need to adjust the hem line. Because A and C were dropped down and out, A is now too short. Draw a line across A, either on the lengthen/shorten line of the pattern piece, or a couple inches above the hem line. Cut across this line. Shift the cut piece down until the hem line of A matches the hemline of C. Tape in place.
Closing the Dart
Because this is a knit pattern with no dart, we now need to remove the dart that was created. It is helpful to tape down piece B. (You can also have A taped down, just do not tape C.)
Close piece C against B on the apex hinge. The original line that had been cut between them is now closed. Place a small piece of tape at the side seam side where B and C meet. Cut the apex hinge open, and continue cutting through the tape stopping just before the side seam. You are OPENING the original apex hinge and creating a new closed hinge where B and C meet at the side seam.
Rotate C on the new hinge. Rotate until the bottom left corner of C meets the 1/2″ line. This maintains the 1/2″ gap, but closes the dart. Tape everything down.
Draw a line around your new pattern piece, smoothing out the edges. Cut out. You are almost done, but not yet!
Finishing the FBA
Lay the original pattern piece on top of the new pattern piece. (Remember how you had two copies of the original?) Align them so they match at the fold, and so that the original pattern piece waist hem point touches the hem of the new pattern piece.
We will re-draw the side seam so that it matches the original waist.
Draw a line from the original waist hem point, blending up to the new side seam. Meet the new side seam below where the dart was closed, so that you are not taking away from the added width given to the bust. (1) Blend the new pattern piece on this line for the finished side seam. (2) Cut out the new pattern piece. (3)
That’s it! This is the final pattern piece with completed full bust adjustment.
At this point it is a good idea to measure the side seam and compare it to the side seam of the back bodice piece of the pattern. Especially for a knit pattern, the difference might be negligible enough to leave, but you may need to lengthen the back bodice side seam to match. Do this on the back pattern’s lengthen/shorten line.
You are done!
It may seem overwhelming when it is new, but practice makes perfect! Once you have done an FBA a couple times, it will feel so much less intimidating. You may want to trace off a couple copies of a bodice pattern and just practice a few times! That way you won’t worry about doing it perfectly the first time. Before you know it, you’ll be doing every FBA with ease.
In the rest of this series, we will cover doing an FBA on a pattern piece with darts, and also a small bust adjustment on patterns with and without darts.
Remember, you’ve got this! And we are here to help. Join our Facebook group for support and encouragement in all of your sewing endeavors!
