ep...it depends on how dense you are quilting it and the size of the project. My machine if it was an actual embroidery design I was using, would tell me how many stitches in the design but I can't remember if the newer ones also tell you the length of thread you need. also, it would depend on how thick the batting. I generally buy cones of threads for quilting rather than spools. I use a lot of Superior's SoFine which I get on the 3,280-yard spools. Yep, they are expensive, but I find that with a few basic colors, I can quilt quite a variety of projects and the cones do last a fair time. I don't quilt densely and usually get 3-4 queen-sized quilts out of cone. I have used a lot of off white, cream, light and medium grey, dusty rose, dusty green, and yellow. Over the years, I added a few lighter colors. When I start to get low, I will watch for sales and try and pick up enough, so I get free shipping. My threads are stored in a dry place out of the sun and light and where they get air circulation as I don't like storing them in plastic enclosed cases. I do not have a local supplier so I do have to order which might take a while if I run out in the middle of a quilt, so I always check how much I have before I start quilting.