Square in a Square Tutorial for Beginners

A square in a square is surrounded by triangles to set a square block on point. The math  formula is given but for convenience a Block Size Cutting Chart is provided.

square in a square quilt block unit

Stitch and Flip Quilting Technique

The stitch and flip quilting technique is used to replace the four corners of a square, making a square-in-a-square. The result is that the inner square is set on point and, once completed, the entire unit is the same size as the starting larger square.

Sometimes called a diamond in a square, a square-in-a-square unit is used in lots of quilt blocks. This Ohio star variation is one example.

Ohio star variation quilt block with a square in a square center unit

Stitch and Flip Math

To make the center unit like in the star block above you start with a large center square and four smaller squares. The smaller squares are half the finished size of the larger square plus a half inch for seam allowance.

smaller squares = half the finished size of larger square plus 1/2 inch

Or expressed another way

smaller squares = finished size of larger square / 2 + 1/2

For example, if you want a 4 inch finished size unit cut one 4 1/2 inch large square and 4 (2 1/2 inch) small squares (4 / 2 = 2 + 1/2 = 2 1/2).

The stitch and flip technique is easy to master. And some say the basic math is too but a size cutting chart is shown after the instructions.

Refer to the Block Size Cutting Chart for the block or unit size you want to make.

Square in a Square Instructions

Step 1 Cut one large square from Fabric A (center square). Cut 4 small squares from Fabric B (background).

I am demonstrating a 4 inch finished size unit. My large square is cut at 4 1/2 inches and my small squares are cut 2 1/2 inches.

Step 2 Draw a line from corner to corner down the diagonal center of all the small squares.

Step 3 With the right sides together, place a small square in two opposite corners of the larger square (Fabric A) and pin in place.

Step 4a Stitch on the drawn line on the small squares.

Step 4b Place the 1/4 inch measurement line of a quilting ruler along the seam line of one small triangle. Use a rotary cutter and cut along the ruler's edge to cut away the corner of the unit. Rotate the unit and repeat to cut the opposite corner.

Step 4c When you finish clipping the first two corners the unit looks like this...

Step 4d Flip what remains of the small squares right side up to reveal the new corners which are now triangles. Press the seams towards the triangles.

Step 5a With the right sides together, place a small square in the remaining two opposite corners of the larger square (Fabric A) and pin in place. Stitch on the drawn line on the small squares. Your stitching lines will overlap the previously stitched on triangles.

Step 5b Place the 1/4 inch measurement line of a quilting ruler along the seam line of one small triangle. Use a rotary cutter and cut along the ruler's edge to cut away the corner of the unit. Rotate the unit and repeat to cut the opposite corner.

Step 5c Now the unit looks like this...

Step 5d Flip what remains of the small squares right side up to reveal the square in a square unit. Press the seams towards triangles.

How to Square Up a Square in a Square Quilt Block

Using this method to make a square in a square unit requires very little, if any, trimming or squaring up.

To start, position the unit so that the inner square is on point. To square up the unit, divide the unfinished size in half. Place this measurement line of a quilting ruler on the vertical center of the unit.

I am demonstrating a 4 1/2 inch unfinished unit. My measurement line to use to square the unit is the 2 1/4 inches (4 1/2 divided by 2 = 2 1/4). Before trimming...

check each point on the inner square to ensure that it has a 1/4 inch seam allowance (indicated by the green lines). Trim the unit if necessary.

Diamond in a Square: Cut Corners Before Stitching

If you're like me you get tired of drawing lines on squares, especially to make a lot blocks for a quilt pattern.  So, I usually clip the corners instead of marking lines before I stitch.

I use the 1/4 inch measurement line of a quilting ruler or the Folded Corner Clipper tool by Creative Grids (R).

Step 1 Place the small squares right sides together with the large square as in Step 3 above. Step 2 Place the 1/4 inch measurement line (for clarity this is indicated by the green line) along the diagonal center of a small square and cut along the ruler's edge. This leaves the 1/4 inch seam allowance. Pin if desired.

Step 3 Stitch a 1/4 inch seam. Flip the corners right side up. Press the seams towards the triangles.

Step 4 Repeat Step 2 for the remaining two corners of the large square. Stitch a 1/4 inch seam.

Step 5 Flip the triangles right side up and press the seams toward the triangles, revealing the square in a square unit.

That's it. The square in a square, or diamond in a square, unit is complete!

Square In a Square Block Size Cutting Chart

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