Secrets to Perfect Fitting Princess Seams: How to Raise or Lower the Curve


Princess seams are popular design lines on many tops, dresses and jackets. Their slimming effect is flattering on almost any figure, but, for them to look just right they must fit the body properly and follow the natural curves of one's bustline. When fitting princess seams, like with so many types of alterations, adjustments must be made well before any patterns are laid out and cut for princess seams to fit properly.

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The most typical types of princess seam adjustments fall into the main categories of a full or small bust adjustment and raising or lowering the seam curve apex. No matter where the princess seams emanate, which can be from either the shoulder seam, armhole or even necklines, any of these types of adjustments are made to the patterns in the same manner.

So, how do you know if the princess seams on your pattern need adjusting?

Recognizing that most commercial patterns are based on a B-cup bustline, if you are either smaller or larger than a B-cup, some adjustments right off the bat will most likely be needed.

The best way to know what type of adjustment is needed is to conduct a careful pattern tissue fitting or to prepare a muslin sample.

Prepare the tissue garment by pinning together the front and side front, then the side back and back pattern pieces. Join the shoulder and side seams and you are ready to test the fit.

Here’s an important tip: Before trying on the half tissue garment, mark the apex of your breasts with either a fabric pen or some tape so they are visible through the tissue. Line up the side seams of the pattern to your body and secure in place with a pin either to a bra or undergarment. Then pin the center front to the center portion of your body at the neckline, bustline and waist. Do the same for the center back – I know this is especially hard to do on one’s self, so get a friend to help.

Any serious fitting issues at this point should become readily apparent.

Too tight, too loose, seam apex in the wrong spot or the lines themselves falling too far to the right or left of the apex are the main types of problems to look for. One common issue is whether the princess seam curve’s apex is in line with the body’s actual breast apex. If the body apex differs from the pattern apex the fit is off and will not look well on the body. If they do not line up horizontally the pattern curve will need to be raised or lowered.

For older women and women with very large busts, the apex on most patterns is much too high and often times have to be lowered. In my example, I have used a small sized dress form with a perky, high bust. The pattern I used has the apex well labeled and as such it is clear to see that the marked apex on the dress form is well above the pattern apex – by 7/8”. Therefore, in this case, the curve on both the center front and side front pattern pieces will have to be raised by that same amount.

(For more detailed guidance on mastering bust modification for the fit you want, join the online sewing class Adjust the Bust: The Complete Guide with Kathleen Cheetham.)

How to raise the princess seam apex on the pattern pieces:

This is a relatively easy adjustment to make with the right tools and workspace. If at all possible work on a cutting mat so the pattern pieces can remain flat and a rotary cutter can be used to make the necessary cuts. The adjustment made in this fashion will not change either the armhole, side seams or bodice length. It only impacts the curve placement so this becomes a fast and easy fix.

What you need to make this adjustment:

Step 1:

Begin by dry-ironing the center front and side front pattern pieces. Lay a large piece of craft, drafting or tissue paper on a table surface or cutting mat. Now lay the pattern pieces side to side onto the craft paper. Line up the bottom notches and any other horizontal lines on the two patterns to ensure they are squarely positioned on the craft paper. If using a gridded cutting mat, use the lines to help square the pieces. To keep them from shifting about hold them in place with either pattern weights, cans or pin them to the paper.

Step 2:

Take a marking pen and draw a perfect rectangle over the curve portions of the two patterns. Start just above the top notch and draw the rectangle to just below the bottom notch as shown in the photo. Secure the pattern to the craft paper with pins both inside and outside the newly drawn rectangle.

Step 3:

With a rotary cutter and ruler (or scissors) cut out the rectangle along the drawn lines. This will separate the prominent curve portions of the side front and center front pattern pieces from the rest of the patterns.

Step 4:

Measure 7/8” up from the bottom line of the rectangle and mark that measurement with a horizontal line.

Step 5:

Place the cut away pattern piece and position it to the new line. Tape the pieces in place. You will notice on my pattern the new pattern apex is now 7/8” higher than the apex label.

Step 6:

The final step is to true the cutting lines of both pattern pieces. Using a French curve or design ruler position it so it lines up with the armhole edges and the pattern apex points and then draw in the new cutting lines.

As a final note, in cases where the curve needs to lower, follow essentially the same procedure, but move the cutout rectangle down rather than up.

FREE Guide: Fitting Fundamentals for Sewers

Fitting Fundamentals for Sewers

Learn fitting fundamentals for sewing breathtaking projects that flatter any body style!Get My FREE Guide»

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Secrets to Perfect Fitting Princess Seams: How to Raise or Lower the Curve