What is a Seam Allowance?A seam allowance begins at the seam you sew to connect two (or more) pieces of fabric or other material, and ends at the raw edges of the pieces you are sewing, usually located to the right of the sewing machine's presser foot. Quilters use a quarter inch seam allowance to sew most quilt blocks and other components together. Exceptions include paper pieced quilts and sewing a narrower or wider seam when you add binding to a quilt with borders (when width doesn't interfere with the 1/4" available at the edges of quilt blocks).
Why is it Important to Sew an Accurate Quarter Inch Seam Allowance?Sewing an accurate quarter inch seam allowance is essential. If seam allowances are off, patchwork pieces will not match-up with each other properly when it's time to sew components together.
You might not notice a seam allowance that isn't quite right when you sew together batches of same-sized squares to make a quilt. If the seams are all the same width, patches will still align correctly. Incorrect seams become a problem when sewing together units with different numbers of seams within their boundaries.
Test Your Seam AllowanceLet's set up your sewing machine to sew an exact quarter inch seam, the standard seam allowance used for quilts. Once you've mastered a quarter inch seam, your blocks will have units with sharp points and crisp corners, and they'll go together easily when it's time to assemble the block or quilt.
Some patterns will tell you to sew a 'scant quarter inch seam allowance.' When you see the term used, make the seam allowance about a pencil-line's width narrower than 1/4" (a scant seam is sometimes necessary for patches to fit together just right, see page 5). Be sure to brush up on your rotary cutting skills and learn important pressing techniques before you begin.
Materials to Test Seam Allowances
- Rotary cutter, mat and 24-inch rotary ruler
- Iron and ironing board
- Sewing machine with a quarter-inch presser foot; use the standard foot if you do not have a quarter-inch foot
- 2 light fabric strips, each 2" x 4"
- 1 dark fabric strip, 2" x 4"
Have extra fabric nearby in case you need more test strips.