Half Square Triangles – Quilt Block Tutorial for Beginners

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.

half square triangle

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.

  1. 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.
pencil line to mark cut line on half square triangle

2. Layer your two fabric squares with right sides together, and the lighter fabric on top. Align the edges carefully.

cut line shown on half square triangle

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.

sew lines on half square triangle

4. Using a rotary cutter and ruler, cut along the marked diagonal line.

half square triangles cut along 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.

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.

11 thoughts on “Half Square Triangles – Quilt Block Tutorial for Beginners

    • Overdale Fabrics says:

      Thank you Elaine, it’s lovely to hear from you and I’m delighted to hear you like this post.
      Happy Sewing Cindy

  1. S. Reid says:

    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.

    • Overdale Fabrics says:

      Thanks for commenting it’s lovely to hear that the tutorial is inspiring. Your idea about accurate cutting is great.
      Happy Sewing Cindy

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