Adding Seam Allowances

Seam Allowances are added to the sewing lines so two or more pieces of fabric can be joined together. The practical minimum seam allowance is 1/4". This provides enough fabric for the presser foot to hold the fabric against the feed dog so it can be drawn through the sewing machine.

When developing quarter-scale prototypes the seam allowance can be 1/4". When a pattern with this amount of seam allowance is scaled up to full size, it becomes a 1" seam allowance. For most full size garments 1/2" is a commonly used seam allowance. This means before it is scaled up to full size, the seam allowance should be reduced to 1/8".

When quarter-scale patterns are scaled up to full size, little or no fitting may be required. However it can be a good idea to add extra seam allowance so the garment can be adjusted in a fitting. More seam allowance is better than less as it can always be trimmed down.

I recommend the following seam allowances for full-size patterns that will include a fitting. Optionally the Shoulder and Side Seams can be just 1". The quarter scale measurements indicate the amount the seam allowances need to be adjusted before the patterns are scaled up.

Note for RTW: Lindsey sews the Underarm / Side Seam last so her clients can have their RTW shirts adjusted for a closer fit. She uses a 1" seam allowance for this combined seam.