Seam and Hem Allowance

Seam allowance preferences vary—some prefer patterns with it included, while others prefer to add it themselves. The preferred seam allowance width also differs. However, basic pattern blocks do not include seam allowance.

When drafting your own patterns, you’ll need to add seam allowance if required.

Personally, I use 1 cm (3/8 in) for standard seams and 0.7 cm (1/4 in) for necklines, unless a collar is involved. If you want extra room for future modifications, consider adding a wider seam allowance.

Some seam finishes require additional width. For example:

• French and flat-felled seams: 1.5 cm (5/8 in)
• Collars: Narrower seam allowance, except at the neckline

Hems also vary based on preference and construction:

• Flared skirts: The hem shape differs at the side seam
• Standard skirts: Usually 4 cm (1 5/8 in), folded once (but 2 cm or 3/4 in is also common)
• Skirt linings & shirts: A narrow hem (1.5 cm or 5/8 in), folded twice

To add seam and hem allowance to a pattern, a standard ruler works well, though specialized seam allowance rulers are also available. A quick online search will show various options.

If curved seams look uneven, don’t worry—you can refine them later. Personally, I often leave my patterns without seam allowance unless I’m working with a delicate fabric that pins might damage. In such cases, I mark the seam and hem allowance directly on the fabric. Various tools exist for this, but if you don’t have one, a regular ruler will do.

And I’ll admit—I often just cut directly without marking the seam allowance at all!

Let me know if you'd like any adjustments! ??