Windmill Quilt Block Pattern

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How to Sew a Windmill Quilt Block

The Windmill quilt block is a traditional design using four half-square triangle units in two contrasting colors arranged to create a beautiful spinning windmill effect. It's a versatile pattern that works in a wide variety of quilt designs and is a great block for beginners to learn!

Materials Needed

• Fabric in two contrasting colors
• Rotary cutter and cutting mat
• Quilting ruler
• Sewing machine and thread
• Iron

Step-by-Step Instructions

1. Cut four 4½" squares from each color of fabric (eight squares total).
2. Take two squares of each color and place them right sides together. Cut each pair diagonally to create eight triangles.
3. Take two triangles of contrasting colors and place them right sides together. Sew along the long edge with a ¼" seam allowance. Repeat to make four HST units. Press seams open.
4. Take two HST units and place them right sides together with seams nested. Sew along one long edge with a ¼" seam allowance. Repeat with the remaining two units to make two halves. Press seams open.
5. Place the two halves right sides together with seams nested. Sew along the long edge with a ¼" seam allowance.
6. Press the final seam open. Your Windmill quilt block is complete!

Repeat these steps to make as many Windmill blocks as needed for your project.

No-Bias HST Technique

This technique eliminates the need to directly manipulate the stretchy bias of the triangle. It uses two easy-to-cut squares and produces two HSTs at once.

Step 1: Draw the Diagonal Line

On the back of the lighter fabric, draw a pencil line diagonally from corner to corner.

Step 2: Sew Both Sides of the Line

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

You will end up with something like this:

Step 3: Cut, Press, and Trim

Press the seam to set it, then press toward the darkest fabric.

Line up the 45° diagonal angle on your ruler with the seam, then carefully trim with a rotary cutter.

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.