For this one, which is a little smaller than a twin-size, I used seven one-half yard pieces of fabric (and another half-yard for the binding) that I cut into 2 1/2 x 43" strips. I then sewed them all together into one very long strip. After that, I just folded the strip in half with right sides together lengthwise and sewed it together with a 1/4" seam. After that, I cut the end so it laid flat, and repeated the process four more times: I put right sides together lengthwise and then sewed it together with a 1/4" seam and then cut the end so that it laid flat (you have to do it or watch someone do it to actually understand how it works).
These jelly roll quilts are so fun to make and super easy. This one took just one afternoon. It sure beats trying to knit something this size, that's for sure.
Here is a link to a video that shows how to do it.
I know it has nothing to do with knitting but I make no bones about being multi-craftual. It's good for the soul.