To work out a different size for your block, use these equations:
For a block using 1/4″ wide white strips:
width of herringbone strip x 3 – 0.5″ = size of (unfinished) block and also length of herringbone strips
For example…. I wrote the tutorial with 4″ wide strips.
4″ x 3 – 0.5″ = 11.5″
So trim your herringbone strips to 11.5″ in length, add the quarter inch white strips between them, and your block will be 11.5″ unfinished (or 11″ once you sew it into a quilt). You can use this to choose what size you want to make your own blocks!
For a block with wider white strips:
Now, if you want to make a GIANT improv block, you’ll probably want wider white strips. The strips in the blocks I’ve shown finish at 1/4″. Use the formula below to figure out your sizing with custom width white strips. (When cutting your white strips out, don’t forget to add 0.5″ for seam allowances.)
(width of herringbone strip – 0.5″) x 3 + width of finished white strips x 2
size of (unfinished) block and length of herringbone strips