A seam allowance is the area between the edge of fabric and the stitching line on two pieces of fabric that are stitched together. Seam allowances have a wide range, the standard one for quilting is 1/4 inch, I often use the 3/8 inch (1 cm) seam allowance, and 1/2 inch is also common in bag making. 5/8 inch seam allowance is standard in sewing apparel.