A seam allowance 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 wide to as much as several inches. Commercial patterns for home sewers have seam allowances ranging from 1/4 inch to 5/8 inch.(From Wikipedia, the free encyclopedia)All garment, quilting, home decorating, hand bag or craft project will have a designated seam allowance. When reading through a pattern before starting (always recommended), look for what the seam allowance is. This measured distance is the width between the ragged edge and where the seam is to be stitched. Sometimes the type of pattern, design, or fabric requirements determines which size seam allowance will be used.
When looking at garment patterns with multiple sizes, the printed lines on the tissue paper are the cutting lines and the seam allowances have already been added.
There are a few garment pattern companies that do not include seam allowances. Burda sewing patterns now include seam allowances on all patterns shipped to English-speaking countries like the UK, USA, Canada, South Africa, Australia and New Zealand. Burda patterns purchased or shipped from Europe DO NOT come with hem or seam allowances.
Sewing industry seam allowances range from 1/4†for curved areas like a neck line or arm hole or hidden seams like facing seams, to 1†or more for areas that require extra fabric for final fitting to the wearer like the center back.
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 the fabric will be safely caught as they are being 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 a small amount of “letting out” space if a garment needs to be just a little bit looser.
When using a serger to construct the seam, seam allowances are cut off. If the pattern may need fit adjusting later, it is a better to serger each of the fabric pieces individuality with a 3-thread overlock. Keep the entire seam allowance in tact by running the edge of the fabric right along the edge of the serger knife. Then seam together the pieces with a regular sewing machine. This way there is still fabric within the seam allowance if the item needs to be adjusted further.
Remember that if the seam allowance is adjusted in one place, it will also need to be adjusted in the corresponding sections. For example, if side seam allowance at the underarm on a bodice is adjusted, the underarm seam allowance on the sleeve or armhole facing will also need the same adjustment.
Check to make sure the seam lines on the throat plate of the sewing machine are accurate to the position of the needle. If you have had trouble with pattern pieces fitting together, it might be in how the fabric is being guided. You can sew on a piece of paper without thread in the needle along the guides on the sewing machine. Measure to see how accurate your sewing is in relation to how you guide the fabric. Make adjustments as necessary to perfect your seam allowances.
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