Quilt Lessons: How to Resize Quilt Blocks

For many quilters resizing blocks is something to avoid. And if you’ve ever tried to resize a quilt block, you know there’s some math involved.  Don’t let that scare you away!

mfq-courthouse-stepsChanging the size of quilt blocks is much easier than it looks. Plus, learning how to modify the size of your quilt blocks can open the door to new quilt design possibilities. Once you know the basics, you can adapt quilt patterns to the finished quilt size you desire.

Resizing quilt blocks just takes a few simple math formulas—no calculus involved!

The first step in modifying any quilt block is to decide the size of your finished quilt block. You can arrive at that choice a variety of ways—doubling a pattern, cutting your pattern in half, or by choosing the size based on the fabric you have available.

Note: When working from a pattern’s cutting instructions, make sure you remove the seam allowance before your double or triple the size. For instance, if your pattern calls for 3-1/2” squares first you’ll subtract the ½” seam allowance, double the finished block size to 6”, and add the seam allowance back in so you cut a 6-1/2” piece of fabric.

Here are the formulas to modify a few basic blocks (taking seam allowances into account):

mfq-9-patchResizing a Square Blocks:

Square blocks are the easiest to resize.  Simply add ½” to your finished block measurement. For example, if you’d like your finished block to be a 4” square, you’ll need to cut a 4-1/2” square of fabric.

Resizing Rectangular Blocks:

Similarly to the square, for rectangle blocks you’ll add ½” to the length and width measurements of your finished block. If you’re doubling block that measures 3” x 4” in your quilt, you’ll cut a 6-1/2” x 8-1/2” rectangle of fabric.



Half-Square Triangle Blocks:

When you want to change the size of a Half-Square Triangle block, add 7/8” to the desired finished block size. To make a 4” finished block, you’d cut 4-7/8” squares.

Quarter Square Triangle:    

Since there are two cut lines and two seam lines in a Quarter-Square Triangle block you’ll need to add 1-1/4” to the desired finished block size. For a finished block that’s 4”, you’d cut you squares to 5-1/4”.

Pin this article to your quilting board on Pinterest or write down these measurements so you can refer to them while quilting. As with everything, after a little practice, resizing blocks will become an easy technique you can utilize whenever the need arises.

For those of us who are visual learners, I’d recommend the free video series called My First Quilt with Sara Gallegos on QNNtv. Start with her “Basic Quilt Math with Squares and Rectangles” video and when you’re ready to try the triangle watch her “Basic Quilt Math with Triangles” video.

What are you waiting for? Log on to QNNtv to start watching select videos for free.

Happy quilting!

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