And here is the quilt math for making up economy blocks, from the blog Catbird Quilt Studio:
https://catbirdquilts.wordpress.com/...h-cheat-sheet/
How does this work? Math. But nothing scary. Bookmark my blog and you’ll be able to find this any time under the Tutorials tab.
"Start with the size of the finished block you want.
finished block size/2 = finished center
example: 7″/2 = 3.5″
finished center + 0.5″ = cut size of center
ex: 3.5″ + 0.5″ = 4″
CUT one center 4″
See note below about fussy-cutting the center.
(finished center/1.414) + 0.875 = size of square to make TWO corners
This assumes PERFECTION. I do NOT assume perfection! Round up at least a half inch.
ex: 3.5/1.414 + 0.875 = 2.475 + 0.875 = 3.350, or about 3 3/8″.
Now round up to 4″.
CUT two squares 4″. [Note: this is a coincidence! You won’t always cut them the same size as the center patch.] Cut two because you need four corners.
CUT each square in half on the diagonal."