How to use Shorten Lengthen Lines
Updated: Sep 17
Working with shorten and lengthen lines is one of those pattern adjustment steps that feels intimidating until you do it once, and then it clicks. They are the secret to keeping the original proportions of a garment (like pocket placement, waist shaping, and hem flares) intact while perfectly matching someone's unique height.
Before making any cuts, gather these essential pattern-drafting tools:
Ruler: Essential for keeping lines straight and measuring gaps.
Paper scissors: Never use your good fabric shears on paper patterns!
Tape: Matte removable tape works best so you can write over it.
Scrap paper: To fill the gaps when lengthening a pattern piece.
A contrasting pen/pencil: To draw your adjustment and blending lines.
The Golden Rule: Always draw a line perpendicular to the adjustment lines across the grainline before you cut. This ensures that when you move the pieces, you can line them back up perfectly without accidentally shifting the pattern left or right.
Because the order of these steps makes or breaks the alignment of your final garment
pieces, always follow this workflow:
Determine your adjustment amount
Compare your personal body measurements (like back waist length, rise, or inseam) to the pattern's measurement chart.
Calculate the exact difference (e.g., "I need to lengthen the torso by 2.5cm/ 1 inch").
Slash the pattern
Cut straight through the middle of the two parallel lengthen/shorten lines. You will now have two separate pieces (e.g., a top bodice section and a bottom bodice section).
Spread or overlap
To Lengthen: (Figure A) Place a piece of scrap paper under the cut edges. Separate the two pieces by your calculated amount. Use your clear ruler to ensure the gap is perfectly even all the way across.
To Shorten: (figure B)Overlap the top piece over the bottom piece by your calculated amount, sliding it up like a shingle.
Lengthen 
Shorten
Align the grainline
Before taping anything down, make sure the vertical grainline (or "fold" line) on both pieces forms a perfectly straight, unbroken line. Tape the pieces securely.
When you spread or overlap a pattern piece, the side seams will almost always end
up with a jagged "step" or a broken edge rather than a smooth line.
To fix this, you need to true the line. Take your ruler and draw a fresh, smooth line
connecting the upper seam edge to the lower seam edge.
On straight seams, simply connect the dots with a straight line.
On curved seams (like hip curves), use a French curve tool or gently freehand a smooth, natural transition line.
Cut away any excess scrap paper or overlap along your new line, and your pattern piece is ready for fabric!
Things to remember
If you have multiple shorten/lengthen lines across pattern pieces e.g., front that has princess seams or multiple panels. remember to lengthen and shorten them all by the same amounts.
If you lengthen a front bodice piece by 2.5cm/1 inch, you must lengthen the back bodice piece by 2.5cm/1 inch at the exact same level. If you don't, your side seams will not match up when you go to sew them together.
Check what lives near those adjustment lines. If a line runs right through a pocket placement marking or a dart, you may need to temporarily trace and move that design feature so it doesn't get distorted when you slash the pattern.
If your garment has a matching neck facing, button placket, or full lining that crosses over the adjustment line, those pieces need the exact same treatment.
Before cutting your fabric, take your adjusted front piece and back piece and "walk" the side seams together on your table, matching them up edge-to-edge. This ensures that your blending (truing) didn't accidentally make one side seam longer than the other.
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How to useShorten Lengthen Lines
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