If I do a small quilt that I can cut the backing all on my table, I rotary cut it. Big quilts I rip my backings since it is easier then laying out the whole length, measuring with a tape measure and then rotary cutting the length. I make sure my backings are about 3 inches bigger all around my quilt top. When the quilting is all done, I rotary cut my quilt edge for the final squaring before binding.