The name pretty much says it all… a square-in-a-square quilt block is made up of four triangles framing a central square to make it look like there’s a square within a square. You may have also seen it used in an economy quilt block (shown on the top left corner in photo below), or in my Plaidful quilt pattern (shown on the bottom left and right in photo below).
This blog post takes you through how to make and trim (or square up) a square-in-a-square quilt block. I also share a few tips and learnings along the way for successful and speedy outcomes.
What You'll Need
Directions & Tips
There are several ways of creating a square-in-a-square unit (or block). The following instructions take the directions from my Plaidful quilt pattern. A lot of the fundamentals from this tutorial, especially when we get to squaring up the square-in-a-square unit can be applied to squaring up these types of units (or blocks) in general.
Here’s how to make and square up a square-in-a-square unit (or block) broken down:
Making Square-in-Square Unit
Step 1: Firstly, on the reverse side of all Fabric A squares, draw a diagonal guideline with a fabric pen or pencil, and cut on it to make a total of four Fabric A Half-Triangles.
Tip: If you’re feeling confident, skip drawing of the diagonal guidelines and jump straight into cutting all Fabric A squares in half, diagonally.
You could also neatly stack up two to three Fabric A squares and cut multiple Half-Triangles at a time.
Step 2: Fold the long edge of each Fabric A Half-Triangle in half and finger press lightly to create a guide. You could choose to use an iron here to press the guide in place, however you may find removing the pressed guide difficult to remove further along, especially if the iron is set at a higher heat level. My preference is to just stick with finger pressing.
To save more time, you can also skip this step and move on to the next one, and at step 4 I’ll show you how you can get away with not carrying out this step.
Step 3: Fold and finger press the Fabric B square in half vertically and horizontally to create central guidelines.
These central guides are used to determine the placement of the Fabric A triangles to frame the central square (Fabric B square). Again, you could use an iron to create these guides. However, I don’t recommend it, as removing them at a later step may be difficult. My preference is to just stick with finger pressing.
Step 4: With right sides together, matching the guides (if you followed step 2), place one Fabric A Half-Triangle on top of Fabric B square. Pin in place as shown in example below.
If you didn’t follow step 2, using the long edge of one Fabric A Half-Triangle, match it up with one side of Fabric B square. Then shift the Fabric A Half-Triangle left or right until the central corner matches the central guide of Fabric B square. Pin in place.
Note: It is okay if the placement of Fabric A Half-Triangle is slightly off in the Plaidful quilt pattern. The pattern is forgiving and has taken in consideration some wiggle room for trimming.
Step 5: Repeat step 4 with second Fabric A Half-Triangle and on the opposite side of the square. You will need to lift up the first Fabric A Half-Triangle in order to match up the guides, especially if you skipped step 2.
Note: It is okay if the placement of Fabric A Half-Triangle is slightly off in the Plaidful quilt pattern. The pattern is forgiving and has taken in consideration wiggle room for trimming
Step 6: Sew ¼in seam allowance on the long side of each triangle as shown. Press the seams open or to the dark side.
Tip: When pressing, take extra care here. You don’t want the heat from the iron to remove the second guideline on Fabric B square (created in step 3). The best way to approach this is only allow the iron to contact the seams and avoid the centre of Fabric B square.
If you happen to remove the second guideline by accident, you could use the pressed seams as a guide, match the two seams and fold Fabric B square in half. Using the seams as the folding guide is more accurate than trying to match up the tips of the Fabric A triangles. This is because sometimes the triangles are slightly off and not completely sewn centrally.
Step 7: Remove excess Fabric A Half-Triangle units on each side as shown with a ruler and rotary cutter.
Don’t skip this step or do it later. These need to be removed to reduce seam bulk and from experience if you perform this at a step later, the excess becomes harder to remove.
Step 8: Pin one Fabric A Half-Triangle on the remaining two sides of Fabric B square by either matching up the central guidelines on Fabric A Half-Triangle and Fabric B square (if you followed step 2), or using the long edge of one Fabric A Half-Triangle, match it up with one side of Fabric B square. Then shift the Fabric A Half-Triangle left or right until the central corner matches the central guide of Fabric B square.
Step 9: Sew ¼in seam allowance on the long side of each triangle as shown. Press the seams open or to the dark side to create one Square-in-a-Square unit.
Tip: Now that all the Fabric A Half-Triangles that frame the central square (Fabric B) are sewn, go over the whole Square-in-a-Square unit to remove the guides created in steps 2 and 3.
Squaring up (or trimming) Square-in-a-Square Unit
Step 1: Square up Square-in-a-Square unit to 3½in square. Squaring up is broken down into two steps. Each part involves removing the right and top sides of the unit (if you’re right-handed) and if you’re left-handed, you’d be removing the left and top sides of the unit at a time.
Before removing the first two sides of the unit:
Using a ruler, line up ¼in above the top corner and ¼in alongside the right corner (the left corner if you’re left-handed) of the centre square and2.
Slide the ruler to match the top and right corner (left corner if you’re left-handed) of the centre square with the 1¾in marks* on the top and right of the ruler (left of the ruler if you’re using a left-handed quilting ruler).
With the ruler locked in place, trim the top and right edges of the Square-in-a-Square unit.
*Now you’re probably wondering where the 1¾in measurement comes from. This is the central point of the trimmed square-in-a-square unit. This central point ensures the square in the middle is centralised and evenly distributed throughout the unit. This is going to vary from pattern to pattern, depending on the final size of the trimmed unit.
Using the Plaidful quilt pattern as the example, the instructions require the square-in-square unit to be trimmed down to 3½in square. Thereby, to find the central point, divide the trimmed square size in two. This equals to 1¾in.
Step 2: Spin the rotating cutting mat or rotate the unit 180-degrees and repeat the previous step with the remaining two sides to complete the square-in-a-square unit.
Tip: The trimming (or squaring up) process can be repetitive and can be quite time consuming. To speed things up, perform each step of the trimming process in batches instead of laying and cutting one unit at a time. For example, lay out a bunch of units on the cutting mat and remove the first two sides of all the units. And then rotate all the units and remove the remaining sides at once.
This wraps up my tutorial on how to make and square up a square-in-a-square unit. I hope you’ll find the tips and tricks along the way are useful and help speed up the process so you can jump to the sewing fun quick! If you’d like to work on building your square-in-a-square skills or would like to give it a shot for the first time, my Plaidful quilt pattern
is a nice place to start. The pattern also explores strip piecing method.
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