Princess Seam Full Bust Adjustment

Trace your side front pattern piece adding all markings.

Draw in your ½ inch seam allowance all the way around your pattern piece.

Mark the fullest part of the bust (where the curve of the bust sticks out the most into the princess seamline). This will be our ‘bust point’.

Draw a line from this point vertically down to the hem.

Draw a horizontal line from the bust point, straight out to the side seam to square it off.

Use a flexible tape measure to measure along the armscye and work out where half way is.

Measure 1 inch further from this half way point is towards the apex (away from the underarm) and draw a mark.

NOTE – For petite sizes, you may need to measure slightly less than 1 inch so that the mark is not too far towards the finished apex. Specifically, for sizes XXS-XS on the Rebecca Page size chart, measure only ½ inch. For size S measure ¾ inch. For sizes M-XL, measure 1 inch.

Draw a straight line from this mark to the bust point.

Half your pattern at armscye and mark 1 inch up towards apex.

That’s all the cutting lines you’ll need. Now it’s time to get the paper scissors out!

Cut from the hem line, up the straight line and out towards the armscye.

Leave a small piece of paper uncut at the top so it forms a hinge.

To get the best possible fit, cut as far as you can towards the edge without cutting through. You will be cutting into the seam allowance. This is ok for this method of FBA.

Cut in from side seam towards the bust point, leaving a hinge at bust point.

Slip another piece of paper underneath your pattern piece.

Move your pattern piece apart, by the measurement you need to increase by, from the hem up to the bust point.

Keep the two parts of the pattern piece parallel and make sure you have the same amount running all the way along this gap.

Cut the bottom 1 ½ inches of the princess line section (the thin section of pattern piece on the right-hand side in the photo) off and keep aside.

NOTE – We’ve used a 1 inch increase as the example in the photo. Please use your own required measurement here as this is where the fullness is added. An approximate guide is 1 inch per bust cup you need to increase by, but this will vary person to person. You may need to sew a muslin to check for your shape and then adjust further.

Move small piece at princess line so that it lines up with the hem of the pattern piece on the bottom, and the princess seam on the right-hand side.

Check the measurement between the pattern pieces is still the same distance from step 3.1.

Tape all pieces down to secure.

Cut around the pattern piece.

When you get to cutting along the gap between the pattern pieces on the side seam, just cut a smooth line from the horizontal line out from the bust up to where the rest of the pattern piece is. We will deal with closing this up specifically in the next step.

To close up dart created at side seam, draw a line through entire pattern from bust point horizontally both left and right.

Cut along this line from the side seam to the bust point only.

Now cut from the princess line along this horizontal line towards the bust point.

Stop just before the bust point so you leave a hinge. Do not cut all the way through.

Close up the dart from the side seam in towards the bust point. Allow the line you cut in step 4.3 to open outwards, so the pattern piece rotates slightly at the bust point.

Tape the pattern together along the horizontal line from the bust point to the side seam.

Trim any excess paper.

Slip a small piece of paper under the hinge from the bust point out to the princess seam.

Tape in place and trim any excess, leaving a smooth line along the princess seam.

To adjust center front panel, line up the center front panel with your side front panel.

We are going to measure up from the bottom of the pattern piece and cut the same lines we cut on the side front piece.

On your center front pattern piece, measure up 1 ½ inches and cut horizontally all the way through the pattern piece. The distance on the center front panel which should match the distance on the side front panel is marked in green on the photo on the left.

Line up the new bottom of your pattern piece with where the pattern piece is on the side front and measure up to the bust point.

Cut straight across the center front panel. and mark the same points, cut across and move same distance. The distances which should match for this cut line are marked in blue on the photo on the left.

Slip paper underneath your center front pattern piece and tape your center front pieces down so that the gaps are the same as on the side front pattern piece.

We have marked on the photo on the right the two distances you need to measure on the side front pattern piece and replicate on the center front pattern piece.

Again, the distances which should match when you tape the pattern pieces down are marked in green and blue on the photo on the left.

When you tape your center front pattern pieces down, make sure the gap is parallel and the distance is the same on both the left and right edge of the pattern piece.

The extra you have added into the waist by moving the pattern pieces apart now needs to be taken out.

This will ensure the waist fits correctly.

Measure the same amount as added in to the pattern piece, from the side seam along the bottom edge of the pattern piece (marked in green). We used 1 inch but use the correct amount for your adjustment.

Draw a smooth line up to the side seam (marked as a blue dashed line).

There is no formula for how far up to draw this line, try to keep it smooth and gentle, while also not going too far up the pattern piece.

The approximate dimensions of what we have drawn on the photo here are accurate, however should you find the ribcage area too tight or loose when you sew your muslin, you may find you need to angle this more or less steeply.

Cut around your pattern piece, following along the blue dashed line.

NOTE – You can do steps 5.3-5.4 before or after step 6. However it needs to be done before cutting your fabric and sewing your muslin or the waist will be too big.

For some bust shapes, this is all you will need to do.

• If you know already that you don’t need any extra side bust coverage, you are finished! Move on to your muslin to check the fit.

• If you know you do need extra side bust coverage, continue on with step 6.

• If you aren’t sure, make a muslin (test bodice out of inexpensive fabric) to check the fit and to see if you need to continue with step 6 or if you are finished.

If you have found from your muslin that you require extra coverage at the side bust, note how much you need to add from your muslin. Here we are using an example distance of 1 inch, but you may find you need more or less.

Place your side front pattern piece onto a piece of paper.

Measure out the distance you need horizontally from the tip of the side bust. Mark this point on the paper and draw a curved smooth line down to the side seam.

You will need this line for later steps. We will refer to it later as the ‘green line’. It is not your finished armhole but is just a guide we will use later on.

Draw on to the paper around the bottom half of the pattern piece (marked in blue on the photo on the left).

Cut along the horizontal line you made in step 4.1 from the princess seam edge of the pattern piece, all the way to close to the side seam. Do not cut through the side seam but leave a small hinge. Do not cut the paper underneath, only the pattern piece itself.

Place your pattern piece back on the piece of paper you drew on in step 6.1. Butt the pieces of paper up against each other as they were. The bottom half of the pattern piece should exactly on top of the blue lines from step 6.2, and the underarm point should match up exactly with your green line from step 6.1

It should now look identical to step 6.1, except that you’ve cut along the line in step 6.3.

Keep bottom of pattern secure on top of your blue lines.

Then rotate pattern at hinge so the armscye is touching the green line you drew in 6.1. It won’t match it, you just want to rotate it far enough that the pattern piece touches the green line at the hinge point from step 1.3 (the marking that is 1 inch past ½ way along the armscye).

Draw from the underarm point up to the hinge (marked in red in the photo on the bottom left). This red line is the bottom half of our new armscye line.

We are now going to create the rest of our new armscye line.

Hold pattern piece in place at the hinge and rotate the top part of the pattern piece so the top of the pattern piece (the apex of the princess seam) meets the green line from step 6.1. The hinge should stay where it was so it is still at the top of your red line from step 6.5.

You will need to move the bottom part of pattern to be able to this. Don’t worry we will move it back later. This is why we drew around it earlier.

Draw from the hinge up to the top of the princess seam (red line).

Continue to draw approximately 1 inch further along the princess seam so that we can reference this curve in the next step.

These red lines are your new armscye. Ignore the green line from now onwards.

Move your pattern pieces back to the blue lines you drew in step 6.2.

Draw a smooth curve from where your red line ended on the princess seam down to the original pattern piece.

Tape your pattern piece back together along the horizontal line, and down onto the paper along the armscye and top of the princess seam.

Cut around the pattern piece, following the red lines for the armscye and princess seam (ignore the green line).

Your side front pattern piece with side bust adjustment is now complete.

You will also need to adjust the center front panel, by the same amount. To do this, draw a straight line horizontally across the center front panel where the panel changes shape near the top. If the panel does not change shape, draw this approximately 1 inch below the top of the pattern piece.

Cut all the way along this marking.

Place the center front pattern piece onto a piece of paper and move the two pieces apart by the same amount as marked in step 6.1 into side bust (for our example we are using 1 inch).

Keeping the gap the same distance all the way along and the pattern pieces parallel, tape the pieces in place.

Draw your new cutting line out smoothly into original piece. Draw a straight line down the center front joining the two pieces.
Cut around the piece and along these lines.

Your FBA is complete! Use these new bodice pattern pieces to make a muslin (a test garment out of inexpensive fabric) to check the fit.