Full Bust Adjustments on Princess Seams

Those of us who are amply endowed in the chest region often have a frustrating time making nice looking darts in bodices. It doesn’t matter how carefully you sew the darned things, they create big wedges of fabric under your arms and dramatic pointy cones shooting out from your solar plexus. That shape may have been chic as all get out in the 1950’s, but its more a source of ridicule these days.

Bullet bras!

The answer to many of our prayers are princess seams, which have the double-benefit of being easier to adjust to accommodate larger bosoms, they also produce a rounder and smoother silhouette.

Princess seams are long seams that run from the waist (or lower) up the torso and either curve towards the armhole or the shoulder seam.

Q. How do you know if you need to do a full bust adjustment (FBA) on a pattern?

A. It depends on the pattern block used to create the design. Most of the well-known pattern companies like Vogue, McCall’s, Butterick and Simplicity design for B cups. If you are larger than a B cup, you will need to perform a FBA.

Q. Why can’t you just use a larger size for a larger bust?

A. If you are larger than a B cup and you select a pattern size that corresponds with your full bust measurement, everything above your bust will be too large. The way a garment fits at the shoulders is key to how neat the garment will look on your body.


Side Front Bodice Pattern
STEPS 1 & 2

Side Front Pattern Piece
STEPS 3 & 4
Side Front Pattern Piece

  1. One inch below the armhole cutting line of the side pattern piece, draw a horizontal line, perpendicular to the grain line.
  2. Mark where the seam allowance crosses this line for the side seam. You will cut along this line starting from the front edge and stopping and the seam allowance mark. You will then cut from the side edge to, BUT NOT THROUGH, the seam allowance mark. This leaves a small sliver of paper to act as a hinge.
  3. Spread the side front apart, being careful not to rip the delicate paper hinge. The general wisdom is to spread it apart one half inch for every cup size larger than a B cup. C cups require half an inch, D cups require one inch, etc. You will likely need to test this out with a muslin and make refinements to your alteration, because you are UNIQUE!
  4. Slip paper underneath the altered pattern and tape it in place.
  5. Trim off the excess paper on the cutting lines on both sides of the piece.


Front Pattern Piece
Front Pattern Piece
Front Pattern Piece
  1. In the corresponding spot on the front pattern piece, draw a horizontal line all the way across the piece, making sure it is perpendicular to the grainline line.
  2. Cut the front pattern piece completely apart along this line.
  3. Put the front pattern pieces on a fresh sheet of paper, tape them down so they are spread apart the same distance as the side front piece along the front curve. Make sure you maintain the grain line when doing so.
  4. Trim the excess paper from the front pattern piece.
  5. Voila! It’s time to sew a muslin and evaluate the fit.


I learned this technique from multiple sources, but refresh my memory by looking at both Sandra Betzina’s Fast Fit and Palmer Pletsch Fit for Real People. I highly recommend adding both to your sewing library.

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My name is Amy Stanton and I am a blogger from Seattle, WA. If you enjoy beautiful photographs, personal essays, book reviews, travel logs, and brag posts about sewing and knitting projects, then we are going to hit it off. ♥

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