Tutorial: Simple Full Bust Adjustment

Blogger: Jenn Meitin Williams

Full Bust Adjustment

With the release of the more adult patterns, we thought it would be a good time to give a quick tutorial on how to do a simple Full Bust Adjustment or FBA for a knit top. For those who are new to the concept of an FBA, a FBA is needed when the full bust measurement is in a different size range than the upper bust measurement.

For example, if the full bust measures a size 8 but the upper bust measures a size 4, one will benefit from an FBA. If selecting a size 8 based on the full bust measurement, the rest of the bodice will be way too big. But if choosing a size 4 based on the upper bust, then there will be pulling across the bust as the fabric tries to stretch to fit.

For your first attempt, make a muslin of the bodice based on the full bust and assses the fit. If there is gaping at the armscye or the bodice feels too big across the upper bust then try the FBA method! 

Let's begin!

First, measure yourself accurately while wearing a bra. Make sure the tape measure is taught but not tight. It may be helpful to have someone help measure so you can stand upright with your arms relaxed at your side.

Determine which size to make using the upper bust measurement, and cut out the pattern pieces. (Note, if you need to grade for the waist, make sure to do that first.)

Hold the front bodice pattern piece up to your body and make a mark approximately at the apex (this is a fancy word for nipple).

Draw a line straight across the bodice -perpendicular to the fold line - through the apex mark.


If using a traced piece of paper, draw in a grainline to match up the pieces later. The grainline should be parallel to the fold.

Cut the bodice pattern piece at the horizontal line drawn through the apex.

Using a scrap piece of paper, tape it behind the bodice to add some length to the front bodice piece. Measure down 1-inch from the apex line and draw a horizontal line.

Tape the bottom bodice piece along that line making sure to line up the grainline.

At the side seam, make a mark half an inch away from the center of the one-inch length that you added as illustrated below.

Draw a smooth curve from the armscye, through the mark, down to a point approximately 2-inches below the added length. Please note, it may take a trial or two to get the perfect fit. You may need less of a “bubble” or a little less added length. Also note, this method really doesn’t work well if adding more than 1-inch of added bust length. Stay tuned for a more involved FBA to be covered in a later tutorial that is better suited for that.

Trim off the excess paper around the new bust “bubble” and at the center fold if necessary.

Now it’s time to cut the fabric! Cut out the front bodice fabric and make two marks where the extra inch was added as indicated by the arrows below. Cut out the back bodice as-is. Do not make any changes to the back bodice piece.


Notice that the front and back side seams are not the same length (because length was added at the bust.) This is ok; we will be easing the back into the front.

Pin/clip the front and back bodice pieces right sides together at the side seams. Start from the bottom and stop pinning when approximately an inch away from the bottom mark.

Now pin from the top of the side seam until 1-inch away from the top mark. There will be excess fabric in between the two pins/clips where you stopped pinning.

Sew the side seam starting at the bottom and when you get to the last pin before the added length (clear clip pictured below); simply stretch the back slightly to make it the same length as the front between the two pins. Sew slowly to attach. This will create a small amount of gathering that will help hold the extra volume in your bust. Because this gathering is under the arm, it will not be noticeable when wearing. It will also be stretched over the bust so it really shouldn’t look gathered once the garment is on.

Once you reach the next pin (orange clip below), finish the side seam up through the armscye.


That’s it! The simple FBA for a knit bodice is complete. This method may not work for everyone, but it is a simple way to start learning for those who need an FBA, and it’s an easy method to try.

We will be covering a more in depth FBA at a later date!

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