Seam Allowance Guide

Its sometimes difficult to know exactly how much seam allowance to pop on our patterns, there are ‘rules’  that apply to this area of pattern cutting, or rather guidelines that you should follow.

Here is some information that I hope will help guide you in making those decisions.

As a general rule, confined or extremely curved areas such as neck line, armhole, and some intricate style seams, will require less seam allowance than straight long seams.

Double or bagged out areas will also require less seam allowance to reduce bulk.

Where a neat inside edge is required, facings are the ideal solution – but we will look at these in some detail in another post.

Some examples of straight long seams in a garment would be:

• A straight skirt hem
• A side seam
• A center back or center front seam

Other factors which can influence the amount of seam allowance (SA) you need:

• Type of fabric – for example a very bulky fabric will require less seam allowance. If the pattern you are using has more seam allowance than you need, you can always trim down the SA after sewing.
• How much a fabric frays – Voile and sheer fabric can fray badly so will need more seam allowance or a french seam, which again needs more SA.
• The stability of the fabric – unstable fabrics that shift around a great deal such as chiffon require more seam allowance,
• Type of seam, firstly in relation to its function, for example does it need to be strong, as in work-wear or jeans. Secondly decoration is also a factor, for example a sheer fabric that is transparent may require a decorative seam such as a French seam and this affects the seam allowance.

When I say ‘more seam allowance’ this could simply mean adding 1.5 cm SA instead of 1 cm SA.

If you are new to sewing and need some practice, here are the links to 3 beginners PDF tutorials on Etsy, the first covers sewing for accuracy and had lots of sewing templates for you to download.

The second covers the very important skills of sewing corners and curves and along with detailed guidance also give the templates you need to create the practice samples.

There is also a third project in this series that covers seam types and also gives you the templates to practice with.

Click on the highlighted links to find these projects.

The method of construction also influences the amount of seam allowance you should add. For example if you are using a serger or overlocker, then you only need the width of the overlocker bite (width of the stitch). This would be the case with knit fabrics.

Below is a table to give you some guidance for woven fabrics:

Seam Allowance Guide

Click this link to download the handy PDF file for Seam Allowance Chart download .

Please note- When producing garments for an industrial setting, small seam allowances are acceptable. Professional machinists are accustomed to sewing with 1 cm seam allowance. However the home sewer requires more seam allowance to produce a garment of high quality.

Some home sewing patterns allow less than 1 cm seam allowance and this makes it very difficult for a home sewer with a domestic machine, the width of the foot and the design of a domestic machine is not ideal for very small seam allowances. It is much better to allow more seam allowance and trim down the excess after sewing the seam.

I hope this helps and if you have any questions or comments then please get in touch.

Happy Pattern Making & Sewing

Nicola x