Seam Allowance

The seam allowance is the strip of fabric between the seamline (where you actually stitch) and the cut edge of the fabric. It's not decorative — it's the margin that lets a seam exist at all, giving the stitching something to hold onto and room for the seam to be pressed, finished, or let out later if needed.

Standard widths vary by convention and by pattern source: many home sewing patterns use 5/8", most European and many independent patterns use 1cm or 1.5cm, and some techniques call for specific widths regardless of the pattern's default — a flat-felled seam needs a wider allowance than a plain one to have enough fabric to fold and enclose. The one universal rule: check what a pattern is using before you cut, because sewing a seam at the wrong allowance shrinks or grows every finished measurement on the garment.

I mark my seam allowance width with tape on the machine's throat plate as a quick visual guide rather than trusting my eye to hold a consistent distance from the fabric edge for an entire long seam — a small habit that keeps seams straight and consistent from the first stitch to the last.