Kiddl & Hoas

In this tutorial I will show you an automated but simple way to add seam allowance to
the outline of a patten piece in inkscape.

Since Inkscape is very similar to Adobe Illustrator, this should also work with it.

Step 1: Draw your pattern without seam allowance

Lets assume you constructed (or traced from an existing piece of clothing) a pattern in inkscape.

Step 2: Duplicate your outline

We need 2 identical copies of the outline (one for the line where to cut and one for the line where to sew).
You can use the Shortcut [Ctrl-D] or choose "Edit --> Duplicate" from the menu.

Step 3: Increase stroke width

Now increase the stoke width of one of the copies to 2 times the width of your seam allowance.
If your seam allowance will be 15mm, you need to select 3cm as stroke with.
Select "Object --> Fill and Stroke" from the menu.
Your image may look a little bit strange now, but don't worry we will fix that soon.

Step 4: Stroke to Path

Now select from the menu "Object -> Stroke to path" to make this 3cm stroke to a regular path with filling. (Shortcut: [Ctrl-Alt-C])
(you can change the fill colour the new object to check whether everything worked OK)

Step 5: Delete inner points

Now select the "Edit path by node" tool (Shortcut: [F2]) and remove the inner points by selecting them and pressing the [Del] key.

Step 6: Set fill and stroke

Now change the fill of this object to transparent and the stroke to 1mm black.
Change the stroke where to seam to dotted.

Now your done.