The half square triangle (HST) is one of the most useful and versatile quilting blocks. It’s also one of the easiest to create, so is perfect for beginners. In this tutorial we’ll look at what they are, an easy method for making them and how to use them to design a quilt.
What are half square triangles?
The HST is a square shaped block, made up of two right-angled triangles of different fabrics. The two triangles join along the diagonal line.
Making half square triangles
There are various methods for making HST’s. Although you can sew two triangles together, it’s easier and more accurate to piece the fabrics together before cutting them. I’ll show you an example of this method below.
You’ll need two different fabrics cut into squares. In this example I’m using two 4-inch squares.
- Take your lighter coloured fabric and place it right side down. Using a ruler and pencil, draw a diagonal line on the wrong side. This line will not show up on the finished quilt block.
2. Layer your two fabric squares with right sides together, and the lighter fabric on top. Align the edges carefully.
3. Sew a seam ¼” either side of your drawn diagonal line. The dashed line in the diagram below shows where you should sew. You can either draw a line to mark where to sew or use a ¼” machine foot on your sewing machine.
4. Using a rotary cutter and ruler, cut along the marked diagonal line.
5. You will now have 2 half square triangle units. Open out each of the units and press them flat. Trim off the small ‘tails’ of fabric.
Using HST’s for a quilt design
Once you’ve mastered this quilt block, you’ll be able to create a variety of quilt designs. Below are some ideas, that use only half square triangles.
Chevrons 
Simple 
Diamonds 
Diagonal stripes 
Rotated squares 
Pinwheel 
Broken chevrons 
Arrow points 
Flock 
Squares in squares
Quilt blocks based on half square triangles
You can also create more advanced blocks based on half square triangles to use throughout your quilt. Here are six ideas for different 4×4 blocks.
I hope you found this tutorial on half square triangles useful. We will be producing more block tutorials in the future. In the meantime, if you have any comments, please leave them below.
These tutorials are a great idea. Thank you!
That’s wonderful to hear thanks Jane.
Happy Sewing, Cindy
Thankyou.Would be interested in future tutorials
Super idea. Thanks
That’s lovely to hear thanks Angela.
Happy sewing Cindy
Brilliant idea Cindy. I usually cut mine with my dies. I just might have faith and cut some up x
Thank you Elaine, it’s lovely to hear from you and I’m delighted to hear you like this post.
Happy Sewing Cindy
Thank you Cindy,
Very helpful and great to see the different ways to achieve great looking quilts.
I’d love a tutorial that helps me achieve accurate cutting then my blocks would fit better. I do try but don’t always succeed.
Thanks for commenting it’s lovely to hear that the tutorial is inspiring. Your idea about accurate cutting is great.
Happy Sewing Cindy
Oh! Wow! This tutorial is so inspiring! Thank you Cindy.
Hi Julie, I’m so pleased you like the tutorial, it’s great to hear.
Happy Sewing Cindy