Finally, here is the tutorial I promised earlier this week which explains how to make accurately sized square-in-a-square blocks.

Square-in-a-square blocks consist of one square with a half-square triangle sewn to each side, creating a secondary square which frames the first. This block is worth mastering as it is the basis for blocks like Ohio Star,

Union Square,

Economy,

as well as a cool way to frame 9-patch blocks.

It also is a go-to alternate block in a lot of quilts.

My preferred method for making this block is to cut the triangles oversized, attach them to the square and then trim the block to size.

The very first time I made one, I cut the center square, complete with perfect (or so I thought) perpendicular edges, but when I went to trim the block after adding the triangles to all four sides, measurements were close, but not spot on—not good enough for OCD me.

Then my science guy husband told me something that messed with my head until I took his advice and it worked out perfectly: The center square absolutely, positively must be perfectly square. And the best way to know if you have a perfect center square is to measure across both diagonals. If the two diagonal measurements are equal, your square is perfectly square.

For my spring quilt, the finished block needed to measure 14″ square. Block construction details generated by Electric Quilt said to cut the center square 10⅜” and two more squares at 7⅞”. I cut the center square as directed, but increased by ⅜” the size of the squares for the triangles. This little bit ensures that, in spite of those four pesky bias edges, there will be sufficient fabric to yield a 14½” block (unfinished size) after trimming.

Once you have your perfect square, take your two smaller squares and cut them in half diagonally to get four triangles.

Find the midpoint of the top and bottom sides of your center square by folding it in half

and finger pressing to make a little crease.

Then fold the two triangles in half, and finger press another crease in the long side—known as the hypotenuse in math circles.

An aside: Has anyone else had the revelation that the math associated with quilting is no longer scary when you can just casually throw around a word like hypotenuse because you finally know what it means? So true that familiarity eases anxiety—plus I live with three geeks, so it’s important to keep up.

Match up the center creases of the triangles with those you made in the center square,

pin, stitch and press toward the triangles.

Repeat the steps to finger press creases in the remaining two sides of the center square

and in the last two triangles,

pin,

stitch,

and press, again toward the triangles.

Now it’s time to trim the excess triangle fabric.

Going with the 14½” unfinished dimension, I aligned the 7¼” marks (half of 14½”) on the ruler at all four points of the gold center square.

Trim the right and top sides first, then turn the unit and trim the remaining two sides, making sure you have a *fat* ¼” of fabric extending beyond the ruler’s edge on all sides. I’ve found that a *slightly* generous seam allowance helps when pressing to one side because of all the bulk at the four corners where the three fabrics come together. Make two of these blocks, sew them together and see if that works for you, too.

My square-in-a-square block was pretty large, which I think increases the chances for error—more fabric, more bias, more fluidity. No doubt, a smaller square-in-a-square block would be a bit easier. I hope this helps you with your future square-in-a-square blocks.

Good luck making yours!