I invite you to dive into the wonderful world of... seam allowances. I've been thinking about writing this article for a while because my beginner students often tell me "it's really convenient that the seam allowances are included"... So yes, that's true but... I still need to tell you a few things to temper this "convenient" aspect at the start of learning to sew and often a bit less convenient afterwards. 

So, let's dive in together! 

1. Definition 

As usual, let's start by defining what we are going to talk about... because basically, what is a seam allowance?

The seam allowance, also called sewing value, is defined as the fabric space between the stitching line and the raw edge of the fabric. It is the space between the two lines drawn on your patterns: the stitching line (where you sew) and the cutting line (where you cut the fabric).

Seam allowance values

As you may have noticed, seam allowance values can vary. They are generally 1 cm but you can find patterns with allowances of 0.8 cm, 1.5 cm, and sometimes these are expressed in inches for American patterns. 

To always make sure you sew at the right distance, use the guides on the needle plate of your sewing machine. 

Don't have guides on your cutting mat? You can use washi tape (repositionable Japanese masking tape) which you stick at the right distance on your mat. Then you just need to align with the edge of the washi tape.

What should you watch out for when buying a pattern?

When you buy a pattern, whether printed or in a magazine, it's important to check whether or not the seam allowances are included. 

Option 1: seam allowances are included 

Often on these patterns, the stitching line is not drawn, you will only see the cutting line. This means you will cut your pieces on the drawn line and you will have to assemble your fabric pieces by stitching at the distance recommended in the instructions. 

Option 2: seam allowances are not included

If the seam allowances are not included, you will need to add them yourself and you can follow the pattern's recommendations or choose your own seam allowance values. The important thing is to be consistent when sewing. 

For my part, to add seam allowances I use a Japanese ruler. It's a tool that has become indispensable to me (to the point where I wondered how I managed before 😅) after my pattern making training. We actually sell them in the shop because they are not always easy to find. 

Why having seam allowances included in the pattern can be practical or, on the contrary, a pain?

As my beginner students say, it’s convenient to have the seam allowances included... indeed, you just have to cut your pieces without adding seam allowances... but that also means the seam allowance value is fixed and if you want to change it, you’ll have to modify the pattern. 

Sometimes, you prefer a 1.5cm seam allowance instead of 1cm, or you want to make a flat-felled seam that requires about 1.5cm while the included value is 1cm... I admit that in this case it annoys me when the sewing lines aren’t drawn on patterns with included seam allowances... 

When you have a pattern without included seam allowances, the sewing lines are drawn. This is very advantageous when you want to:

• Grade the pattern, meaning increase the size. For example, you need a size 50 but the pattern only goes up to 48. Having the sewing lines makes it easier to grade the pattern.
• Alter the pattern. For example, you have a sweatshirt with classic sleeves and you’d like to change it to raglan sleeves; this is totally possible if you work with the sewing lines. 
• Choose the seam allowance values depending on the pieces. For example, it’s not uncommon when I sew a men’s shirt to add different seam allowances depending on the pieces. 
• ...

Okay, but what should I choose now? With or without seam allowances?

It all depends on your level, tastes, and personal preferences.

If you’re a beginner, it’s unlikely you’ll start by grading or altering your patterns... So included seam allowances are really very practical. 

As you progress in sewing, you might want to add your creative touch, make pattern modifications, choose your seam allowance values... and for that, nothing beats having the sewing lines and therefore a pattern without included seam allowances! 

Personally, as you’ve probably guessed, I prefer a pattern without seam allowances, but that’s largely due to my sewing experience as well as my love for pattern making and beautiful finishes (I like being able to choose the seam allowances depending on the type of sewing I’m going to do, especially when sewing lingerie)... so I’d say it really comes down to personal taste and expectations for this wonderful creative hobby that is sewing!  

So get your pencils, Japanese ruler, needles, and washi tape ready! 

Happy sewing!