Accurate Piecing Along the Way: Squaring Up Blocks and Quilts

QuiltNotes Learning Center

Last Updated November 12, 2018

This article is a request from a dear friend, Maggie. She asked me, “When and how do I square up my quilts and blocks?” She is not simply asking how to trim a block or quilt top. Instead, she is asking how to make blocks with straight sides and square corners that fit together with ease.  Additionally, she wants a quilt top that lays flat. In my opinion, when to check for accurate piecing is every time you cut or sew fabric. How to check for accuracy is simple as well, use the lines on your cutting mat.

Cutting for Accurate Piecing

Accuracy starts with the cutting process. If fabric is cut to the wrong size or in the wrong direction, there is no way your blocks will be square. Let’s take a simple 4-patch and see what a difference 1/8″ makes.

accurate piecing blocks

The 4 patches on the left are cut 2-1/2″ x 2-3/8″. The 4 patches on the right are cut 2-1/2″ x 2-1/2″. The difference between the two sets is each of the patches on the left are 1/8″ smaller on one side only. You might think that 1/8″ is not a big deal.

accurate piecing 4 patch

Use a 1/4″ seam allowance. Press the seams to one side before sewing the next seam. If they are cut correctly, each of these blocks should measure 4-1/2″ x 4-1/2″.  You can see the difference between the two blocks in the size and shape. There is no way these blocks, along with 10 or 20 more, will ever fit together correctly. Squaring up the block on the left will only make matters worse. The block on the right requires no trimming at all.

A 1/8″ difference here and there may not seem like much. When you multiply 1/8″ times 4 seams or 20 or 50 seams, the difference is huge! For tips on cutting, check out these articles:

Cutting Direction

What I mean by cutting direction is the grain line in fabric. There are three grain lines:

  • Lengthwise – runs the length of the fabric, parallel to the selvage.
  • Crosswise – runs across the fabric, perpendicular to the selvage.
  • Bias – runs in a diagonal direction between the lengthwise and crosswise grains.

The Learning Center contains several articles on grain line you should check out:

I have found that using fabric starch and washing fabric produces more accurate and enjoyable piecing. I resisted both for many years but once I tried them, I couldn’t be happier. Especially when sewing bias edges, fabric starch is your very best friend. Check out these articles:

Sewing for Accurate Piecing

You have heard it a thousand times, use an accurate seam allowance. I suggest using a scant 1/4″ seam allowance. A scant allowance is just a thread or two smaller than the measured allowance. This difference helps accuracy when pressing the seams. There are countless tools out there to help you measure and achieve a consistent, accurate seam allowance. Check for a 1/4″ presser foot for your machine. Read the article, 9 Tips for Frustration Free Machine Piecing.

Accurate Strip Piecing

Strip piecing is so popular but it can be frustrating. One of the most common problems are strip sets that bow in the center. On way to prevent bowing is to change stitching direction each time you add a strip. Sew the first two strips together from left to right. Sew the next strip from right to left and so on. Check out these articles on strip piecing:

Wavy Borders

I can’t tell you how many quilts I’ve seen that were perfect before the borders were added. If you take a long strip of fabric, piece it to one side of the quilt then cut it off at the bottom, your borders will wave like a flag in the wind. You may not see it, but if you measure the edge, it will be longer than it should be. If you lay the quilt on a flat surface without carpeting, you will see it.

If you want flat borders, you have to measure and cut to size. The article, Lengthwise Grain Binding and Borders has a section on cutting and attaching borders. This is how I do every border for my quilts.


Here are some ways to achieve accurate piecing at every step:

  1. Take the time to prepare and wash the fabric for cutting.
  2. Cut accurate pieces.
  3. Use a consistent, accurate, scant 1/4″ seam allowance.
  4. Check accuracy each time you cut the fabric or sew a seam.
  5. Press seams in one direction.

I hope you have enjoyed this article. Most of all, I hope these tips help you achieve more accurate piecing and eliminate the need for squaring up blocks or quilts.

For more project tutorials and videos:

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