Quarter Square Triangles – what a handy block! Quarter Square Triangles (QSTs) can come in a few forms. You might know them as hourglass blocks or perhaps the hybrid Split Quarter Square Triangle. Let’s take a look at them all, with a downloadable Quarter Square Triangle chart thrown in for good measure!
Quarter Square Triangle Variations
Just so we’re all on the same sheet of music, this is what I mean by QST, hourglass and Split QST blocks (see photo below).
Hourglass blocks are Quarter Square Triangle blocks made with only two fabrics, which creates the hourglass silhouette. Or a bow tie if you read it from side to side instead of up and down. (A)
Quarter Square Triangles have four different colour fabrics in the block. (B)
Split Quarter Square Triangles are made with 3 fabrics and consist of one large triangle and two smaller triangles. (C)
How to sew Quarter Square Triangles
As the name suggests, the QST block is simply four triangles sewn together to give a square.
You could by all means cut four separate triangles and then sew them together to form the Quarter Square Triangle block.
This method is handy if you need an exact layout (you want to know the position of all the fabrics). It’s important to remember to cut your individual triangles such that the straight grains of the fabric are on the outer edge of the block. If the bias grain is on the outside you run the risk of stretching. If you cut your triangles from each fabric like this, you’ll be fine:
This method makes it easy to sew a specific unit but it can be a pain to sew bias edges together. Also, if you need a small block the tiny individual triangles will be a bit tricky to handle. For these reasons I prefer to make my Quarter Square Triangles from Half Square Triangle blocks, and that’s what I’m going to show you today.
To make the Hourglass variant of a Quarter Square Triangle you’ll start with 2 oversized squares which you’ll use to make 2 identical HSTs. You will then sew the 2 HSTs together and cut them apart to yield 2 identical hourglass blocks.
When you’ve made your 2 HSTs it helps to press the seams both toward the same fabric. Then put them right sides together, but with different colours opposite each other (the seam will nest). You can see the purple faces the mauve below, and the seam is nested.
Draw a diagonal perpendicular to the direction of the seam, as seen below. Make sure it is at 90 degrees to your seam, otherwise you’ll have trouble maintaining your points in the corner.
Sew a seam a quarter inch either side of the drawn line. Cut the units apart along the drawn line and press your hourglass units open.
So 2 squares make 2 HSTs, which are then used to make 2 hourglass blocks. Don’t worry, I’ll talk about starting square size and trimming a bit further on.
Quarter Square Triangles
This “true” Quarter Square Triangle is made from 2 different HSTs blocks, instead of 2 identical HSTs.
The process is the same – the HSTs are placed right sides together, seams nesting, with a diagonal drawn perpendicular to the HST seams. Two HSTs will yield two QSTs.
One thing to note here is that the 2 Quarter Square Triangles produced will NOT be identical – so keep that in mind when you’re planning your design.
Split Quarter Square Triangles
This nifty little unit is made by replacing one of the HST units with a solid square.
The HST unit is placed right sides together with the square and a diagonal is again drawn perpendicular to the HST seam. One HST and one square will yield 2 SQSTs.
Again, the 2 Split Quarter Square Triangles produced will NOT be identical – they are mirror images.
Quarter Square Triangle Chart
Let’s talk about the size of the starting squares needed to make Quarter Square Triangle blocks.
I make my Quarter Square Triangles the same way I make my Half Square Triangles – oversized. I prefer to make them a little on the large size and then trim them back to give really accurate blocks.
If however you’ve perfected your quarter inch seam and really don’t like trimming, then you can create your Quarter Square Triangles with this formula:
Starting square size = finished QST size + 1-1/4″
So if you want a 4″ QST when it’s sewn into a quilt, you’ll need to start with four 5-1/4″ squares.
If you’re like me and want a bit of breathing room so you can trim your QSTs back to size, then use this formula instead:
Starting square size = finished QST size + 1-1/2″
So if you want that 4″ QST then with the oversizing method you’ll need to start with four 5-1/2″ squares.
Here’s a handy Quarter Square Triangle Chart that lists the starting square sizes for various QST sizes (for the oversized method).
If you’d like a printable version of this chart you can fill in the boxes below and I’ll email it to you. You’ll also get some handy extra emails that will show you where to find some of my other tutorials and downloadable quilting projects.
Quarter Square Triangle Trimming
Firstly, I recommend using a square ruler when trimming your Quarter Square Triangles. I have this one* (below) and it’s fantastic for blocks 6″ and less because of that high density area of lines which makes it easier to pinpoint the centre of your block.
There are two important things to look for when you trim your blocks:
1. Correctly measuring your centre point, and
2. Making sure the diagonals are 45 degrees at the corners of the block.
The centre point of the block will be at the half of the measurement of the unfinished block. So back to our 4″ QSTs:
A 4″ finished QST is 4-1/2″ unfinished. Half of that is 2-1/4″. So you’ll want to put the centre point of your block under the intersection of the lines 2-1/4″ from the edge of the ruler.
The red arrow, below, show the block centre point at 2-1/4″. The black arrows show where the diagonals hit the block corners (remembering the block will be trimmed to 4-1/2″).
It’s important the diagonals are bisecting the corners and you may have to wriggle/rotate your ruler a bit to make this happen. It’s not always possible to get all four corners spot on, but do your best to make them all as accurate as you can.
Having trouble with your triangle diagonals not meeting at the corners? You might need to pay more attention to when you draw your diagonal line on the back of your HSTs. Remember how I mentioned it needs to be perpendicular to the HST seam? Even if it means your line isn’t exactly from corner to corner when you draw it, you want to make sure the line is 90 degrees to the HST seam to create four even quadrants in your block.
I’ve also included the trimming size (unfinished size) on the downloadable chart, as well as the centre point location. It’s good to have all the info in the one place.
What to make with Quarter Square Triangles
Peta of She Quilts A lot adapted the queen to a crib quilt (below) by only using 4 of the Fleur blocks – isn’t it fantastic!
I hope you get the chance to experiment with Quarter Square Triangles soon. Be sure to drop me an email and show me what you’ve made!