I'm really lousy at figuring out how much fabric to buy.

Can someone help me figure out how much fabric to get for each color to make 20 blocks please?

Here's the square...

http://www.quilterscache.com/W/WeathervaneBlock.html

Using http://vrya.net/quilt/classic.php for calculations, I get

color 1: 1.375 yards
color 2: 1.5 yards
color 3: 1.375 yards

for 20 blocks, 12" (finished) each, no sashing, no borders, no binding, and no backing. I'd get extra, but I always cut my HST's a bit bigger and trim to size. Nice block!

no guarantee, but here's what I'd do. You'll also need some for a border.

Check out page 2 of your link. More information and just what you are asking about.

There is a picture of the quilt AND a list of Supplies.

Yes, I used page two for the measurements of the block pieces. The list does NOT include measurements for the sashings and borders included in the quilt pictured. Binding and backing are not included either, nor would I expect them to be. Overall, the pattern is given for the Block, not the Quilt. Marcia is merely showing an example of what can be done with that particular block, not providing a quilt pattern.

THANK YOU!! :D