“Sewing two layers of fabric together to make a seam is the foundation of every other sewing technique.” – The Sewing Answer Book *affiliate
Two important elements of a seam are the stitching line and the seam allowance. The seam allowance is the space between the stitching line and the cut edge of the fabric. These two elements have a wide variety of options that are used for different purposes. Here are a few examples:
A straight stitch with 5/8” seam allowance.
A serged seam with ¼” seam allowance.
A quilt block with ¼” seam allowances.
Seam allowance will fluctuate depending on the project. Most garment patterns, like from “The Big 4”, will use 5/8” unless stated otherwise. The Big 4 pattern companies are Simplicity, Vogue, McCalls, and Butterick. Some patterns designed for knits have ¼” seam allowance. Also, lingerie patterns often have ¼” seam allowance. In quilting the seam allowance is ¼”.
In the pattern directions the seam allowance will be listed.
Why are there different seam allowances?
For garments, a wider seam allowance provides room for adjustments if they are needed. You can let out each side seam ¼” and that will add 1” to the total circumference of the garment. One inch may not seem like very much, but it can mean the difference of “a bit too tight” and “just right”. Trust me, I let out the waist of my couture cocktail dress exactly that much and it made it feel perfect.
Here is a good place to mention that in couture very generous seam allowances are used. A 1-1.5” seam allowance provides room for any future alterations. The garments are meant to last a lifetime and over a lifetime someone’s body will typically change. For example, the garment can be adjusted to fit wider hips after childbirth.
For garments made from knit fabrics, the seam allowance may be ¼”. Ready-to-wear knit garments are often sewn with a serged seam. This stitches the seam line and finishes the seam allowance all in one pass.
When quilting, a ¼” seam allowance is used. This helps to reduce bulk in the quilt and conserves fabric. The addition of the quilting stitches helps strengthen the seams to last a long time.
These examples are only a sampling of variations, but they are the most common. The next step after learning about seam allowance is seam finishing techniques. I’ll be covering a few of my favorite seam finishing techniques soon, so be on the look out.