Squaring up your quilt blocks before you begin sewing them together will ensure a beautifully finished quilt with a perfectly flat top and squared corners. It also will help you avoid the problem of the sashing or the borders not fitting, and the frustration of working around your mistakes. While there are different methods for squaring up fabric, rotary cutting is a fast and easy way to square up quilt blocks. It is accurate because the fabric is held flat with a square ruler and not raised by a scissor blade. Follow these instructions to cut a square quilting block.
To square up the fabric you will need a rotary cutter, a cutting mat and a cutting ruler (also called a square ruler). Select a rotary cutter that fits comfortably in your hand. Cutting mats come in different sizes, but a 24" x 36" is the most practical for quilting blocks. Rotary-cutting rulers are made of thick transparent acrylic and a good one is marked in increments of 1", 1/4" and 1/8."
Place your quilt block on the cutting board. Put the square ruler over the block so that the block measure you desire is in the upper left corner of the quilt block. For example, if you are making a 6" block, the number 6 on the ruler will be in the upper left, and the corner of the ruler where the two 1s meet will be in the upper right corner of the block.
The ruler should be as close to the top and right edges of the fabric as possible and still cover the sides of the block entirely. For a 6" block, the left side of the block should be either on the 6" line or just a little beyond it. If your block does not reach the 6" mark, it is too small. You should not see any part of the cutting board under the upper and right edge of the ruler.
Using the side of the square ruler as a guide, trim any fabric extending past the top edge with the rotary cutter. Then trim any excess fabric on the right edge of the quilt block.
Rotate the quilt block until the corner you have just cut is aligned with the correct block measure on the ruler. Again, trim any fabric extending past the top edge and then the right edge of the quilt block with the rotary cutter.
You now have a perfectly squared quilting block.