Square-in-a-Square Quilt Block Pattern

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How to Sew a Square-in-a-Square Quilt Block

The Square-in-a-Square quilt block is a classic and versatile design featuring a center square framed by four corner triangles. It can be used to create intricate designs by varying colors, fabrics, and placement — and it's a great choice for quilters of all skill levels!

Cutting Guide

For a 12" finished block, cut one 6" center square and four 3" corner squares. Adjust sizes proportionally for other finished block sizes.

Step-by-Step Instructions

1. Cut your fabric pieces. Cut one large center square and four smaller corner squares. The sizes depend on your desired finished block size.
2. Mark the diagonal lines. Using a fabric pen or pencil, draw a diagonal line on the wrong side of each corner square, from corner to corner. This is your sewing line.
3. Place the first corner square. Place one corner square right side up on one corner of the center square, aligning the edges. The marked diagonal line should run from the center of the corner square to the corner of the center square.
4. Sew the first corner square. Sew along the marked diagonal line, starting and stopping ¼" from the corners of the center square.
5. Trim and press. Trim the excess fabric from the corner square, leaving a ¼" seam allowance. Press the corner square open, away from the center square.
6. Repeat with the remaining corners. Repeat steps 3–5 with the remaining three corner squares.
7. Trim the block. Trim to your desired finished size, using the center square as a guide. Make sure all four sides are even and square.

Your Square-in-a-Square quilt block is complete! Repeat these steps to make as many blocks as needed for your quilt.

How to Resize Quilt Blocks

The first step in modifying any quilt block is to decide on your finished block size. You can base this on doubling a pattern, cutting it in half, or working with your available fabric.

Note: When working from a pattern's cutting instructions, remove the seam allowance before scaling. For example, if your pattern calls for 3½″ squares, subtract the seam allowance (½″), double the finished size (3″ → 6″), then add the seam allowance back (½″) — giving you a 6½″ cut piece.

Resizing Square Blocks

Add ½″ to your finished block measurement. For a 4″ finished square, cut a 4½″ square of fabric.

Resizing Rectangular Blocks

Add ½″ to both the length and width. To double a 3″ × 4″ block, cut a 6½″ × 8½″ rectangle.

Resizing Half-Square Triangle Blocks

Add 7/8″ to the desired finished block size. For a 4″ finished HST block, cut 4⅞″ squares.

Resizing Quarter Square Triangle Blocks

Add 1¼″ to the desired finished block size. For a 4″ finished block, cut 5¼″ squares.