Sewing 101: Seam Allowances

Sewing 101: Seam Allowances

Created by: Nikki Johnson of

Welcome to our new Sewing 101 series, where we'll highlight basic sewing techniques for beginners that are also a great refresher for more advanced sewists. If you have a sewing technique you'd like us to highlight in this series, please let us know in the comments section. Today is all about seam allowances!

Knowing what seam allowances are and how execute an accurate seam allowance is arguably the most important part of sewing (aside from selecting the perfect fabric). Without an accurate seam allowance, your project can end up too large, too small, or too… disastrous.

Whether you primarily quilt, sew garments, or home décor – they all use seam allowances.

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There are three standard seam allowances:
  • ¼”
  • 3/8”
  • 5/8”

Sewing 101 Seam Allowances

The 3/8” seam is usually the first line, the 5/8” the second. Your machine may be different. A ¼” seam is primarily used in piecing quilts. 5/8” is the standard seam allowance for sewing apparel. And you’ll see a 3/8” seam allowance in various sewing circles, including garments and other sewing projects. Always check your pattern or tutorial for seam allowances before starting! You can get yourself into some seriously hot water if you don’t, or at least some quality time with your seam ripper.


For an accurate ¼” seam, you will need a good ¼” piecing foot. Some of them will be exactly ¼” wide, and some of them will have markings showing you where your ¼” seam should be. Others have handy guides to keep your fabric in the right place. Mine is clear with red markings.

Sewing 101 Seam Allowances

For quilting, many (including myself), recommend using a scant ¼” seam. This is to allow a little ease for your fabric once your seam allowances are pressed properly.

This is a ¼” seam:

Sewing 101 Seam Allowances

This is a scant ¼” seam:

Sewing 101 Seam Allowances

You’ll notice that the standard ¼” seam is right on the ¼” line on my piecing foot. The scant ¼” seam has a little bit of space between that red line and the fabric.

When I started using scant ¼” seams instead of standard ¼” seams in my quilting, my accuracy increased exponentially! I was suddenly creating blocks that were the right size, instead of a little bit too small! It’s up to you, though. Test which one gives you more accurate results and go from there.


The wonderful thing about sewing machines is that they have markings for 3/8” and 5/8”. Some have more. If they aren’t properly labeled, you can always use a trusty ruler, seam gauge, or other measuring tool to figure out which is which.

Sewing 101 Seam Allowances

The 3/8” marking on my machine is the first one. Keep your fabric on that line for an accurate seam, and don’t stray!

Sewing 101 Seam Allowances


This is the standard seam allowance for sewing apparel.

Sewing 101 Seam Allowances

This leaves lots of room for alterations, tweaking, and a variety of seam finishing techniques. This is also the widest seam allowance you will usually find specified in sewing projects – except perhaps for home decor projects.

Sewing 101 Seam Allowances

Happy Sewing!

Sewing 101 Seam Allowances

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