Basic techniques for shortening or lengthening a pattern.

The two methods presented below allow you to make a whole range of modifications, and this on any type of pattern. You will then be able to easily modify the pieces making up a skirt, pants or even a top. 

In both cases, the modification to be made must be carried out in a coherent manner in order to be able to assemble the new pieces together without difficulty. Thus, if the front is modified, the back must also be modified so that the side lines match perfectly. If the height of an armhole (on the bust) is modified, the sleeve head (on the sleeve) must also be modified.

Method A : the objective being to preserve the complete structure of the pattern

The size and volumes of the garment are not changed.
Cut the pattern pieces in 2 and add or subtract the desired value between these 2 parts.

Key point: for ease, use graph paper. The lines will serve as a guide to respect the parallel and perpendicular.

• Using a ruler and a criterion, draw an axis perpendicular to the straight grain and to the front and back centers (if the pieces have them) on the parts of the pattern to be modified. To place the line, refer in more detail to the explanations concerning the modification to be made. But in general, it is advisable to avoid placing the line on reference lines, assembly notches or even darts.

  

• Cut along the line to divide the pieces into 2 parts.

  

At this point, you should have defined the value to add or subtract.
 

To lengthen a pattern

• Glue a piece of paper under the top part of the pattern.

• Transfer the measurement to be added onto the paper, starting from the cutting line of the piece.

• From this new reference point, draw a new axis parallel to the cutting line.

• Glue the lower part of the pattern onto the paper, aligning the cutting line with the axis drawn previously. Check that all parts are still perpendicular to the straight grain and to the front and back centers (if the pieces have them)

To shorten a pattern

• Transfer the measurement to be subtracted onto the pattern, above the cutting line.

• From this new reference point, draw an axis parallel to the cutting line of the pattern.

  

• Glue the lower part of the pattern to the upper part, aligning the cutting line and the axis drawn previously. Check that all the parts are still perpendicular to the straight grain and to the front and back centers (if the pieces have them).

  

For a lengthened or shortened pattern

• Trace the sides in a straight line or a curved line according to the original outline of the pattern.

  

Check that the assembly lines between the different parts match perfectly and that there are no offsets.

Method B : The goal is to change the width of the bottom proportionally to the desired change.

Lengthen/shorten the bottom of the patterns in line with the existing outline. 

Concrete cases

It is best to use this technique sparingly so as not to alter the ease of a piece.
Shortened hampered line
The amplitude is increased on the bottom.

Extended shackled line
The width is reduced on the bottom.


Shortened flared line
The width is reduced on the bottom.

Extended flared line
The amplitude is increased on the bottom.


Shortened straight line
The magnitude remains intact.

Extended straight line
The magnitude remains intact.

How to lengthen a pattern

• First, check that there is enough paper under the parts to be modified so as not to run out of space.

• Using a ruler and a yardstick, transfer the value to be added under the hem line of the pieces concerned. Repeat this operation several times at regular intervals.

• Join all of these points by drawing a line. To do this, it is advisable to use a modeler's ruler called a "parrot" to draw the curved lines. This operation can also be done freehand, provided that you have transferred a very large number of reference points.

• Extend the lines on both sides of the new outline, without changing their inclination. Check that the intersection between the side lines and the hem line forms a right angle.

• Check that the assembly lines between the different parts match perfectly and that there are no offsets.

How to shorten a pattern

• Using a ruler and a yardstick, transfer the value to be subtracted above the hem line of the pieces concerned. Repeat this operation several times at regular intervals.

• Join all of these points by drawing a line. To do this, it is advisable to use a modeler's ruler called a "parrot" to draw the curved lines. This operation can also be done freehand, provided that you have transferred a very large number of reference points.

• Check that the intersection between the side lines and the new hem line forms a right angle.