If there's an online calculator or chart that would help, please let me know!

I want to make a twin size quilt, the pattern I want to use is 8 inch blocks. How many 8 inch blocks do I need to make the quilt! I will do borders too, but I do not intend to put sashing between blocks.

Would seven blocks across by nine blocks down give me a good starting point before adding borders?

(7 x 8inch blocks - seam allowances = ??)

(9 x 8 inch blocks - seam allowances = ??)

What is the size of a twin quilt??

Thanks for any help!!