I always go a scant plus I use Aurifil thread. I used to have problems doing the civil war blocks that finish at 6 in but was always coming up short. My teacher told me about the Aurifil. The difference is that its only 2 threads instead of the normal 3 so its more accurate; especially when doing so many small seams in one small block. I was surprised when my blocks started coming out closer to the correct finshed size. Pressing your blocks really well also helps them come to size, I don't stetch them. Things that stretch will eventually stretch back.