Quarter Square Triangles

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!

Learn to sew Quarter Square Triangle, Hourglass and Split Quarter Square Triangle blocks

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)

Quarter Square Triangle, Hourglass and Split Quarter Square Triangle quilt blocks

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.

Quarter Square Triangle format and split quarter square triangles

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:

Sewing quarter square triangles

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.

Hourglass blocks

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.

Hourglass quilt blocks (quarter square triangles)

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.

How to sew quarter square triangle blocks

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.

How to make quarter square triangle quilt blocks

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.

Hourglass block (how to sew this quarter square triangle variant)

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.

Quarter Square Triangle quilt blocks

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.

Quarter square triangle diagram

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.

Split Quarter Square triangle blocks

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.

Split Quarter Square Triangles

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).

Quarter Square Triangle Chart with cutting and trimming sizes

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.

Best quarter square triangle ruler

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″).

Quarter Square Triangle trimming tips and Trimming Chart

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.

Quarter square triangle trimming tips

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

I’m biased, but I think you should make my Fleur Queen or Fleur Mini pattern! They both use SQST blocks.

Fleur Mini:

Fleur mini quilt pattern PDF - by Kirsty of Bonjour Quilts

Fleur Queen:

Fleur queen sized quilt pattern PDF - by Kirsty of Bonjour Quilts

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!

Peta of She Quilts A lot made this version of my Fleur quilt pattern

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!



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35 thoughts on “Quarter Square Triangles”

  1. My goodness! I had the basic idea of this technique, but I was lost in the woods about how to make it end up the size I needed it to be when I finished. These instructions really sorted it out for me!!! No more making do or laying awake doing “quilt math” in my head. Thank you so very much

  2. Thank you! I knew there was an easier way than cutting 4 squares into 4 triangles each and sewing all those triangles together and this confirmed it! Same size squares starting out too. Thanks so much!

  3. You are always generous & awesome to share your tips. I find there are a few of you “pro’s” out there who want us to learn & be as good as you are. You remember to give us every detail so as we get it exactly accurate. That’s the point right? Thanks so much, I’ve learned alot from you!

  4. This is really a great post Kirsty. Thanks a bunch. Just printed the chart so I can keep it close by. I know these sorts of tutorials take a bit of time to create and I so appreciate your doing this for all of us!!

  5. thank you for the great instructions on the QST. I am making a 12 1/2″ smaller and needed to know how to reduce those in the block. I think this will help me get the size I need.

  6. Thank you for making it clear and easy to follow. We are using these directions in a small group, and it will make our patterns much easier! Also thank you for the chart. I did the math, but it was nice to have confirmation that I did it right!

  7. Thanks for sharing. It’s always nice to get a refresher on the basics. What is the pattern in the picture with the cat from the email? That looks really nice.

  8. Thank you so much for your clear tutorials. I wish I had had these 10 years ago when I started patchwork. Still useful so I am saving all, particularly the tables.

    I also like your patterns but catching up on unfinished projects since a house move disrupted my sewing life!

  9. That certainly takes the mystery out of QST! Thank you for the tutorial and for that all-important chart. I have the HST down pat, but these would throw me for a while, so the chart is very helpful. My eyes aren’t terrific, so I will have to try to enlarge it for my wall without distorting it. I hope that is okay.

  10. Kristy, Thank you for a great tutorial. The only think I found confusing was: Being a math major, I found where you mentioned fractions to be confusing. For example, 4 -1/2″is 3 1/2″ to me. Once I caught on to your method, it was fine, but at first I found it completely confusing. I found the tutorial to be extremely informative and beautiful otherwise. I have bookmarked it for futher use. I appreciate the tip about making sure the marked line is exactly perpendicular. I don’t think I’ve had that problem and it’s nice to know where to look, if I do or to be able to help someone else. You are very generous to give help to others. I appreciate your reference to a great ruler. Many of the rulers do not offer 1/8″ markings and sometimes I just need those on my ruler. I appreciate it when someone takes the time to give me a link to great product. I love the Fleur patterns and hope that I can come back and get one of them soon. I have lots on my plate right now. My children’s father just had two seizures, fell and broke the two columns in his right hip that supports the socket in his right hip. He had two surgeries this week so that the columns could be rebuilt in his pelvis. Each were major surgeries, two days apart. During the second surgery, the surgeon also redid the hip replacement that had already been done. He had messed up the hip so badly that the surgeon had no place to put the socket and had to create the place to put it. Hopefully this coming week, he’ll be moved to a rehab facility for an estimated 10 weeks. So, it’s been crazy drama for 2 weeks and will be for some time. Piecing isn’t even on my mind yet. Thanks for a great tutorial that took my mind off the drama. That’s what I like about quilting and looking at the beautiful work of others. Thanks, thanks, thanks.

    • What a lot you have on your plate, Susan. I’m happy I could help just a little with a bit of distraction. I hope all the surgeries go well and that he has a good recovery.
      Take care!

  11. I love the way your blogs are clearly written and straight to the point. They really help me
    identify why I have trouble with some processes. Thank you for doing such a great job!

  12. How kind of you to share all of this wonderful information! I’m a newbie quilter (and new grandma) anxious to shower my darling little granddaughters with quilts. Thanks ever so much, Kirsty!


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