Close Window

Tips for Changing Quilt-Block Sizes

One of the questions I get asked repeatedly is how to change the size of a quilt block. It's actually pretty easy if you know a few basics. But before I get into that, I'd like to introduce myself. I'm Carolyn Beam, the new editor of Quilter's World and the person who will be writing this update. I've been quilting for a long time and have been in the quilt publishing business for over 15 years. Quilting is my passion and my obsession! I have a large studio with my office at one end, so I am constantly surrounded by all things quilting. It's my happy place! In these monthly updates I'll be sharing my thoughts about quilting with you, and I'd love to hear ideas and suggestions from you as well.

In each update I will select a book or pattern that I think will be of interest to you. With this update, I'm suggesting the Exclusively Annie's X Marks the Spot quilt pattern. This would be a good pattern for you to try your hand at changing a block size. Can't you see a pillow made from one larger block to accompany this quilt? Or maybe you'd like to make a one-block wall hanging. I see lots of possibilities with this pattern.

The first thing to do when looking at a block to be resized is to understand how the block is constructed, or what might be called the "grid" of the block. Let's look at some examples. A Pinwheel block is really just a simple four patch made of four units -- two patches by two patches. That is, there are two patches in each of two rows. A Shoofly block is made up of nine patches constructed in a three-by-three grid; all the divisions are the same size even though five are plain squares and four are assembled units. A Sawtooth Star block is made up of 16 patches constructed in a four-by-four grid with all divisions the same size.

Click here for larger image Click here for larger image Click here for larger image
Pinwheel Shoofly Sawtooth Star

We'll use these examples when we talk about block size and resizing the blocks. When referring to block size, it's usually the finished block size without the outer seam allowances. These blocks are easy to resize because all divisions are the same size.

Let's start with the Pinwheel block. Because this block is a two-by-two grid, it easily fits into any even-number block size: 4 inches, 6 inches, 8 inches, etc. To figure out the size of each unit, divide the finished size by the number of divisions in one horizontal row.

For a 4 x 4-inch four-patch block: 4 inches divided by 2 divisions = 2 inches. That means each unit needs to finish at 2 x 2 inches. Then add the seam allowances to get the size to cut each patch. When using a standard 1/4-inch seam allowance, for plain squares add 1/2 inch and for half-square triangles (HSTs) add 7/8 inch. This means that for this 4 x 4-inch block, the HSTs need to measure 2 7/8 inches on two sides (cut two 2 7/8-inch squares from fabric and then cut each one in half once diagonally for four HSTs).

Let's say we want this Pinwheel block to finish at 12 x 12 inches: 12 inches divided by 2 divisions = 6 inches. Each unit needs to measure 6 x 6 inches finished (each HST will need to measure 6 7/8 inches on two sides when cut).

You might ask if this would work for an odd-number-sized block. Yes, it does: 9 inches divided by 2 divisions = 4 1/2 inches. That means each unit needs to finish at 4 1/2 x 4 1/2 inches. The cut size for the squares that are cut once diagonally to make the HSTs is 5 3/8 inches (4 1/2 inches + 7/8 inches).

Let's look at the Shoofly block. This block fits easily into any size divisible by three: 6 inches, 9 inches, 12 inches, etc. To figure out the size of each unit, take the finished block size and divide by three (the number of same-size pieces/units in each row).

For a 12 x 12-inch block: 12 inches divided by 3 divisions = 3 inches. Each piece/unit will need to finish at 3 x 3 inches. To figure the size to cut each patch, add the appropriate amount, assuming 1/4-inch seam allowances: 1/2 inch for squares and 7/8 inch for half-square triangles.

Would this block work if you wanted your finished block to measure 20 inches? Let's see: 20 inches divided by 3 divisions = 6.666 inches; that's not an easy size to work with. It would be best to either make this block 18 inches or 21 inches, both of which are easily divisible by three.

For the Sawtooth Star block, since it has an even number of divisions, it works best with even-number block sizes. Unless you like to work tiny, go with larger block sizes that easily divide by four: 8 inches, 12 inches, 16 inches, etc. The math for in-between even-number sizes for the Sawtooth block works easily too: 10 inches, 14 inches, 18 inches, etc.

If you wanted a 16 x 16-inch finished block, 16 inches divided by 4 divisions = 4 inches. Each piece/unit needs to finish at 4 x 4 inches. For the cut size for each patch, add the appropriate amount, assuming the standard 1/4-inch seam allowance: 1/2 inch for squares and 7/8 inch for half-square triangles.

For an 18 x 18-inch Sawtooth Star block: 18 inches divided by 4 divisions = 4 1/2 inches. That means the cut sizes are 5 inches for plain squares and 5 3/8 inches for half-square triangles (on two sides) after adding for seam allowances.

Click here for larger image

What if the center to the Sawtooth Star was made of smaller patches as shown in the drawing? For a 16 x 16-inch block, each finished division is 4 x 4 inches, as we've stated above, and in the example shown there are four smaller divisions (2 divisions in each row) in each 4-inch red-white unit. That means 4 inches divided by 2 divisions = 2 inches. Each red or white patch is 2 inches finished. Adding seam allowances, cut 2 1/2-inch squares from each fabric to achieve the correct finished size.

We'll try one more example for this block: For a 20 x 20-inch block, 20 inches divided by 4 divisions = 5 inches. Each unit is 5 x 5 inches finished. So, the center patches are 5 inches divided by 2 divisions = 2 1/2 inches finished. As before, add the seam allowances for the cut sizes.

Of course, not all blocks have pieces/units that are the same size, like this basket block.

Click here for larger image

You can still determine the grid by counting the number of divisions in the block. There are five equal divisions. For a block with five divisions, the easiest sizes to work with are block sizes that are divisible by five: 15 inches, 20 inches, 25 inches, etc.

How do you figure the unit sizes for each? Let's look at a 15 x 15-inch block: 15 inches divided by 5 divisions = 3 inches. Each unit is 3 x 3 inches finished.

The small square at the top left is one 3-inch finished piece (3 1/2 inches unfinished). The small half-square triangle units finish at the same 3-inch size. The rectangle is one division by three divisions: 1 x 3 inches = 3 inches, 3 x 3 inches = 9 inches or 3 x 9 inches finished (3 1/2 x 9 1/2 inches unfinished). The large half-square triangle center unit is three divisions: 3 x 3 inches = 9 inches finished. Add the appropriate seam allowances for each piece.

There are some blocks, like foundation-pieced blocks, appliqued blocks, blocks with curved patches, or eight-pointed star blocks that don't work using this method. For blocks like these, the easiest way to change the block size is to use a copy machine to enlarge or reduce the block drawing. Once you reach the finished size you want, cut the copy apart and add seam allowances to each piece of the pattern.

Once you've practiced these techniques, you'll be able to change many block sizes to suit your needs. In the next update, we'll look at enlarging a slightly more complicated block and making a quilt that can be used as a baby quilt, table topper or wall quilt, depending on your fabric choices.

Back to top