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The Secrets to Perfectly Square Quilt Blocks

Squaring up a quilt block — trimming a block to its unfinished measurements with straight edges and tidy 90-degree corners — is the final step in completing your block. Very few quilters sew a perfect block, and some patterns are not even designed to be completed without trimming as a final step.  That’s why squaring up a quilt block is an important skill for quilters.

Square Quilt Blocks on Cutting Mat

From Clever Curves: Piecing Techniques with Toby Lischko

Do you need to square your quilt block?

In a dream quilting world, you’d never need to square your quilt blocks. Each unit would be cut to the perfect size with sharp edges and points, and all your seams would be exactly ¼”. In that case, your block should come out to a perfect square!

But let’s be real: Sometimes your cutting and piecing isn’t so perfect. When that’s the case, you need to determine whether squaring the block will help.

Can your block be fixed with squaring?

First, look at the seam allowances

Did your block come out too small overall? This is likely caused by too large or irregular seam allowances.

If this happens to you frequently, aim for a scant ¼” seam. Traditional patchwork uses a scant 1/4″ seam allowance so that the completed block is slightly oversized. Then the quilt block can be trimmed to the correct size.  As your patchwork skills improve, less and less trimming will be necessary.

Second, look at the points in your block

Before squaring, check if your patchwork includes points (such as these star points) near the outside edges of the block.  Each point should have a ¼” allowance at the block raw edge.

If you trim away these ¼” seam allowances when squaring up a quilt block, you’ll end up sewing over the points when you pieces two blocks together. Ultimately, your quilt will have dull points.

Working with these challenges

If your block is overall too small or if you stand to lose vital ¼” seam allowances at points, reconsider your approach before squaring up quilt blocks. 

Depending on the design of the block, you might decide to square to a smaller size than original planned. A 12″ block could become a 11½” block, for example. As long as your block sizes are consistent throughout the quilt, that will work fine!  

If, on the other hand, your block has outer points that you don’t want to dull, I suggest you do not trim away vital seam allowances. Instead, attempt to join blocks without squaring and aim to  improve your patchwork skills to avoid this dilemma in the future.

Square Nine Patch Quilt Blocks

4 ways to square up quilt blocks

So you’ve decided that it’s a safe bet to square up your block. Great! What next?

There are a few different approaches for how to square a quilt block, and the one you use depends on how the block is constructed.

Cutting around all four sides

The easiest way to square up most quilt blocks is to cut around all four sides with a square-shaped ruler. Ideally, you’ll remove just slivers of fabric to bring the block to ideal, square dimensions. Use this approach for most traditional patchwork blocks designed to finish as squares.

With a ruler that matches the size of your block.

For this method to work, you need a square ruler whose dimensions match the unfinished dimensions of your block. If you’re making a 12″ unfinished block, you need a 12″ square ruler.

Squaring with a Square Shaped Ruler

Place the ruler on top of the block on a cutting mat. Center the ruler on the block, using the block’s design elements to make sure it is straight and aligned. Hold the ruler firmly in place and trim around block to square. 

Read more about this method here.

With an oversized ruler

Don’t have a ruler in the exact size of your block? No problem! All you need is a ruler that’s bigger than the block’s unfinished dimensions.

Using Tape when Squaring Your Block

Choose two edges of the ruler to use; then use masking tape to clearly mark the correct, trimmed shape directly on the ruler. For example, if you’re making a 5″ square block, place the tape on the 5″ mark, both vertically and horizontally, on the ruler to create a 5″ square on the ruler.

Place the taped ruler over your block. You can use the edge of the masking tape like the edge of a ruler, helping you center the ruler over the block.

Trim along the real ruler edges. Then, turn the ruler 180 degrees, match the trimmed edges to the tape edges and trim again along the real ruler edges to finish.

Read more about this method here.

With an undersized ruler

What if you have the opposite problem: Your unfinished block is bigger than any of the rulers in your sewing room? We have you covered!

In this method, you trim the block one quarter at a time by aligning a specific point on the ruler with the center of the block.

First, identify the center of the block if it’s not clear from the piecing. Divide the block’s unfinished measurement in half, and use that measurement to align the ruler with the center of the block. Trim the two edges of the block, but only to where the ruler ends. Rotate and repeat on all four corners.

Read more about this method here.

Without a square ruler

If you don’t have a square ruler at all, you can still square up your block with extra legwork.  Instead of relying on a square ruler shape, use your cutting mat lines.  

Choose a particular spot on your mat to visualize the correct, trimmed shape. If necessary, you can mark that space with masking tape or washi tape. Then, place the block on the cutting mat so that it’s centered over the trimming space.  Cut around it along the mat measurement lines without moving the block.

Cutting perpendicular edges

Square rulers work great for square blocks, but not all blocks are intended to be square. Some finish as rectangles, and many improv-style blocks are freely pieced without specific sized elements. When you square such a block, you must create order where there may have been none.

Trimming an Improv Block 

In each of these cases, cutting perpendicular edges is the smart approach for squaring your block. Begin by establishing one 90-degree corner on your block. Then use that corner as a reference point for cutting the block to desired size.

Here’s how:

  1. Trim one edge of the block, making your cut parallel to any key block elements.  Remove as little fabric as possible in this first cut.
  2. Cut along an adjacent edge, creating a 90-degree corner. Again, remove as little fabric as possible.  Now your block has one square corner.
  3. Align the squared block corner with perpendicular cutting mat lines.
  4. Cut the remaining edges of your block by measuring from the trimmed edges to the desired unfinished block size.  

As you gain experience squaring up different kinds of quilt blocks, this step will become increasingly instinctive. And, as your patchwork skills improve, squaring even becomes less necessary. Keep sewing and you’ll keep growing!


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Sue Simon

Could you tell me the name of this quilt block? It is lovely! Love the curved seams!

Lorraine Cooper

Hi Sue I am just a subscriber and I noticed your comment. The block is from Bluprint lesson course with toby lischko
Clever curves and piecing techniques and it has all the detail you need with excellent instruction and templates. I have nothing to gain by recommending you take Bluprint classes but I went from a person who had made childrens school uniforms over 30 years to a competent quilter. I do apologise fpr my typing as I am legally blind. But yes I still quilt


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