Seam allowance (sometimes called inlays) is the area between the edge and the stitching line on two (or more) pieces of material being stitched together. Seam allowances can range from 1⁄4 inch (6.4 mm) wide to as much as several inches. Commercial patterns for home sewers have seam allowances ranging from 1⁄4 to 5⁄8 inch (6.4 to 15.9 mm).
Sewing industry seam allowances range from 1⁄4 inch (6.4 mm) for curved areas (e.g. neck line, armscye) or hidden seams (e.g. facing seams), to 1 inch (25 mm) or more for areas that require extra fabric for final fitting to the wearer (e.g. center back).