How to Square-Up a Quilt Block

When making a quilt, you might have to square-up or trim a block or unit so that it has the correct measurements before being joined to the rest of blocks or units.

Usually, quilt patterns will give you a bit of extra fabric when, for example, stating the size of a square for a Half-Square Triangle. This is done in case your seam allowance is not 100% correct or if when pressing, some of the fabric gets lost within the crease or fold of the seam.

As an example, if you stitch together two 5'' squares to create two 4'' HSTs, you will end up first with two HSTs measuring 4 ½'' each. If your desired measurement as mentioned is 4'', you need to get rid of that excess and I will show you now how :)

Trimming a block

First technique: with a square ruler and washi-tape

1. We are going to start with a 4 ½'' x 4 ½''  square block that needs to be trimmed down to a 4'' x 4'' block. For that, you need to first place two strips of washi-tape or cello tape along the 4'' lines of your ruler and an extra small piece of tape, where the centre of the square is.

Square up quilt block tutorial

2. Then, mark with a fabric pen/chalk or Frixion pen the centre of the block on the fabric itself. Match the centre of the block with the centre of the square and trim the right and top sides of the block.



3. Now, rotate your block twice to the right and place again your ruler on top of the block, matching the mark on the fabric and the centre of the square. Trim again the right and top sides of the block, which should measure 4'' on all sides.




This technique can be used not only with Half-Square Triangles, but any square-shaped block as shown in this example.

Second technique: with a special ruler for HSTs

If you love making Half-Square Triangles, I totally recommend you getting a special ruler like the one you can see below. Mine is from Quilt in a Day and it is perfect for trimming HSTs.

1. Using the same measurements as with the first technique, before pressing my HST open, I place it on the table as shown with the ruler on top.

Half square triangle ruler square up block

2. My finished block needs to be 4'' x 4'', so the stitching line on the block needs to match the 4'' line on the ruler. The extra fabric appearing at both sides of the triangle is the one that I need to trim with my rotary cutter.

Half square triangle ruler square up block

Half square triangle ruler square up block

This way I also achieve a perfect 4'' x 4'' square!

Half square triangle ruler square up block

And that is it for this tutorial. You can practice trimming-down squares or HSTs with the Kaleidoscope Quilt pattern.

I hope you found this post interesting :) Thank you for reading and I will see you back here soon.

Happy quilting!


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