Tutorial: Full Bust Adjustment

Blogger: Jenn Meitin Williams

Full Bust Adjustment

With the release of more women’s patterns, we thought it would be a good time to provide a quick tutorial on how to do a Full Bust Adjustment (or FBA) for a knit top. If you are new to the concept of an FBA, let us enlighten you! LLK patterns are drafted for a B cup; which means the full bust is 2 inches larger than the upper bust. A FBA is needed when the difference in the full bust and upper bust is greater than 2 inches.

For example, if a full bust measures 37.5 inches (size 8) but the upper bust measures 34 inches (size 4), then a FBA is needed because the difference is 3.5 inches. If you make a size 8 based on the full bust measurement, chances are the rest of the bodice will be way too big. If you choose a size 4 based on the upper bust, then there will be pulling across the bust as the fabric stretches to fit. Alternatively, simply grading out for the bust will not give you a proper fit. If desired, make a muslin of the bodice based on your full bust and see how it fits. If there is gaping at the armscye or it is too big across the upper bust then try this FBA method!

Let´s get started!

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

Once you have bust measurements, choose your size based on your upper bust measurement and cut out that bodice. (Note, if you need to grade for your waist, make sure you do that first.)

Hold the front bodice pattern piece up to your body and make a mark approximately at your apex (This is a fancy word for your 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. Once the scrap paper is taped to the top portion of the bodice, measure down 1-inch from the apex line and make another horizontal line. One inch is a good place to start if you are unsure about how much length to add. If the difference in your upper bust and full bust is 3 inches (a C cup), you may need a little less length added. If the difference in your full bust and upper bust is 4 inches (a D cup), then 1 inch might be perfect

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 your bust so it really shouldn’t look gathered once you have the garment on. Once you reach the next pin (orange clip below), finish your side seam up through your armscye.

That’s it! You did a simple FBA for a knit bodice. This method may not work for everyone, but it is a simple way to start learning if you 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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