Originally Posted by
grammy Dwynn
Are you quilting or sending to quilter? For 'most' LAQ's you will want it approx 8 inches larger, both directions. So for your 48 inch square quilt you will need it to be approx 56 inches back. That means you will only need approx 12 inches more. If it was me, I would go for the 56 length first, which is 1.5 yards. Now if you want the back to be all the same fabric, then you would need a total of 3 yards.
Next options ~ do you have left overs from piecing the front? You could piece something to make up the 12+ inches. I have split the my 44" down the middle and put other fabric in the middle, so I have 3 sections in the back. Also I usually take a 1/2" seams for my back piecing.
Grammy Dwynn has it right. Also, if your quilt is going to a LAQ, most of us prefer the seams to run across the quilt rather than from top to bottom. If the seams on the backing (especially the long ones) run from top to bottom, I will load the quilt on it's side so the seams don't build up on my rollers - that creates tight strips with hammocks of material inbetween, which is great for tucks in the fabric, but not good for quilting. This turning of the quilt is not a big deal for hand-guided LA quilting, but it could pose a problem for someone who uses computerized quilting and the pattern chosen is directional (I haven't done enough quilting with a computer to know how to fix that, but I'm sure it can be done!)
Personally, I love pieced backs that are as interesting as the top.