Square-in-a-square block

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,

Ohio Star

Union Square,

Union Square

Economy,

Economy

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

9-patch

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.

To accurately check the diagonal measurement of your square, align the 45-degree line of your ruler along its bottom edge, positioning the ruler’s edge along the diagonal of the square so that it intersects the corners of the square.

To accurately check the diagonal measurement of your square, align the 45-degree line of your ruler along its bottom edge, positioning the ruler’s edge along the diagonal of the square so that it intersects the corners of the square.

Check the measurement. Mine was 15-11/16".

Check the measurement. Mine was 15-11/16″.

Repeat the steps above to take the measurement along the other diagonal.

Repeat the steps above to take the measurement along the other diagonal.

15-11/16"—a perfect match with the other diagonal.

15-11/16″—a perfect match with the other diagonal.

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

sq-in-sq5

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

sq-in-sq6

and finger pressing to make a little crease.

sq-in-sq7

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

sq-in-sq8

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,

sq-in-sq9

pin, stitch and press toward the triangles.

sq-in-sq10

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

sq-in-sq11

and in the last two triangles,

sq-in-sq12

pin,

sq-in-sq13

stitch,

sq-in-sq14

and press, again toward the triangles.

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

sq-in-sq15

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.

Up close and personal: all the corners, clockwise from upper left: top, right, bottom, left.

Up close and personal: all the corners, clockwise from upper left: top, right, bottom, left.

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.

sq-in-sq17

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!

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