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How to Add and Subtract Seam Allowances in Illustrator

How to Add & Subtract Seam Allowances in Illustrator

UPDATE 2/11/14: This method is only accurate  on very basic shapes like rectangles and squares. I have discovered a new, very accurate method which I detail in my Pattern Workshop course.

Have you ever wondered how to add or subtract a seam allowance in Illustrator?

For years, I added seam allowances to my pattern pieces manually.




I laugh because now I now know it’s so, so easy to let Illustrator do the work of adding seam allowances for me. And now, lucky you…I’m going to show you how to do it! But first, I want to let you in on the plan for the next few weeks.

I know a lot of you are really looking forward to the grading tutorial – the one where I actually show you how to take one pattern piece and grade it up and down (and all in between) to create all your pattern sizes. Patience, ladies! Hehe, just kidding. But seriously. PATIENCE! When I started writing the outline (yes, there’s more to the tutorials than just turning on the camera and BAM!) for that doozie of a tutorial, I realized there were a lot of things some of you might not yet be familiar with. And if I were to try to teach you all those thing sin one tutorial, well, Vimeo would probably explode with the video upload size.


I did a series of mini tutorials to acquaint you with some really awesome and useful features in Illustrator – stuff that I use all the time when grading patterns and designing stuff for my blog. Here’s the schedule:

  • Tuesday, December 10 – How to Use the Measure Tool in Illustrator
  • Wednesday, December 18 – How to Use the Align Tool in Illustrator
  • Thursday, December 26 – How to Set up Preferences in Illustrator
  • Friday, January 3 – How to Measure Curved Paths in Illustrator (sleeve caps, armholes and necklines, oooh la la!)

Unless you already feel super confident in Illustrator, I highly encourage you to take the time to view these tutorials as we lead up to the bigger ones. They are only 5-10 minutes each, and you might learn a cool trick or two. Pinky swear!

With that, let’s get to adding and subtracting those seam allowances!

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  • abby @ thingsforboys

    Ah, so simple!

  • Jenn AJennuineLife


  • Aafke

    Well, this wil make life much easier :-)