Patch As Patch Can Quilt Block Pattern

New to quilting? Check out our beginner quilting class covering all the basics.

How to Sew a Half Square Triangle (HST) Quilt Block

This technique is great for making half square triangles because it eliminates the need to directly manipulate the stretchy bias of the triangle. It uses two easy-to-cut squares and produces two HST blocks at once.

Materials You Will Need

• Fabric (at least two different colors or prints)
• Ruler
• Rotary cutter or fabric scissors
• Sewing machine
• Iron and ironing board
• Pencil or fabric marker

Step-by-Step Instructions

1. Cut two squares of fabric to the same size. For example, cut 5-inch squares for a 4-inch finished block.
2. On the back of the lighter fabric, draw a pencil line diagonally from corner to corner.

3. Stack a pair of light and dark squares right sides together. Sew a ¼-inch seam allowance on each side of the diagonal line.

4. Cut along the marked diagonal line to separate the two triangles. You will end up with something like this:

5. Now cut along the diagonal line.

6. Press the seam together to set it, then press towards the darkest fabric.

7. To trim the block to the exact size, line up the 45° diagonal line on your ruler with the seam.

8. Carefully trim your block with a rotary cutter.

9. Repeat these steps to create as many HST blocks as you need for your quilt.

How to Resize Quilt Blocks

The first step in modifying any quilt block is to decide on the finished 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 doubling or tripling the size. For example, if your pattern calls for 3½" squares, subtract the seam allowance (½"), double the finished block 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.