Sarah in Brooklyn

I'm getting ready to order fabric for sashing my first large project and I want to make sure I have enough. Can you please check my math?

I'm making 80 4" squares, and I want 2.5" sashing around each block. I'll be using cornerstones, too.

So I figure 4 sides x 80 squares = 320 4" strips = 1280" of strips

1 yard of fabric = 560" of 2.5" strips

1280/560 = 2.3

So 3 yards is WAY more than enough, right?

Oh, and I figure for 8 x 10 rows I'll need 90 cornerstones.

Thanks for helping. I really want to get this right the first time!