Here's a block that looks complicated, but is actually quite easy to make. It can be made in Holiday colors for a festive quilt, or more traditional colors. The block looks like this when it's complete:

What size is it?

Create this block any size you see fit. Simply assign a size to each unit of the block. Imagine a 4x4 grid over the block. If you assign 1 " (finished) to each unit of the grid, the block would be 4x4" finished. If you assign 2" (finished size) to each unit of the grid, the block would be 8x8 " when done.

Instructions - How do I go about making it?

Break the block down to simpler construction units. If you analyze it, you'll see that it's four units that look like this:
Break that down further, and you'll find two units like this:

Let's tackle the green/white unit first. Quilter's use a 1/4" seam allowance. If we decide on a 2" finished grid, we'll need to cut 2-1/2" strips of white and green. Seam them together lengthwise and carefully press the seam allowance to the green side. Cut them across into 2-1/2" units and set them aside.

Now the red/white unit. Cut a 2-1/2" strip of red fabric, and sub-cut into 2-1/2" x 4-1/2" units. For each block you make, you will also need 8 2-1/2" squares of white. Lay one of the white squares on one end of the red fabric, right sides together, lining up the raw edges. Stitch across the white square diagonally and carefully press back. You may choose to trim out the extra white fabric from under the corner unit, or trim off both the exta red fabric and the white fabric, or don't trim at all. If you are machine quilting, the extra fabric thickness isn't going to trouble you.

Repeat for the other end of the red/white unit:

Now stitch the green/white and the red/white units together. You will need four units for each block - they rotate 90° clockwise around the center point.

How do I use it?

You can use these pinwheel blocks side-by-side. It looks almost like peppermint candy, doesn't it?

Or you could use sashing, creating nine patches between the pinwheels:

Something to thing about ...

Set the blocks on the diagonal with plain blocks for a nice wiggly look. They almost dance, don't they?

Add a secondary block for an interesting graphic look. See how those secondary blocks create four patches between the pinwheels, and they seem to interlock with each other, sharing their corners? A bonus!

Related : More Free Block Patterns - Quilt pattern with pinwheel blocks