Your needle size depends on the thread weight. Visit Superior Threads website, they have charts that tell about needles and threads, what the different threads are used most often for & what needle to use with what thread. As for thread weight for quilting, it depends on how much you want the stitching to show. Heavier thread ( 12 weight up to about 30 weight) are pretty heavy ( thick) threads. Common people seem to choose a lot are 40, 50 & 60 weight. 60 being pretty fine thread. The needle has to be the correct size for the thread