Why is 5/8″ (1.5cm) the standard seam allowance?
A 5/8″(1.5cm) seam allowance provides enough “extra” between the seam line and the cut edge of the fabric to make sure that you will safely “catch” the pieces that you are joining together. This is particularly important when working with fabrics that ravel easily. A 5/8″ (1.5cm) seam allowance is also easier to work with when pressing a seam open or topstitching it for a finishing touch. Finally, it also provides you with a small amount of “letting out” space if you should need to make your garment just a little bit looser.
