When you learn how to make half square triangles (hst’s) you will find that there are many ways of doing this. I have listed four of them in this half square triangle tutorial, beginning with the most basic method and progressing through three more ways that make more hst’s each time.

The first point to note is that because you are cutting squares to make these half square triangles, you need to begin with larger squares to allow for the additional seam allowance no matter which method you use.

### Half square triangle tutorial – method one

The most basic method is to cut two squares in half along one of the diagonals and then sew two triangles from different fabrics back together again using a 1/4″ seam along the long edge. Press the seam allowance towards the darker fabric and trim the corners where the triangle tips stick out.

You will need to begin with 2.7/8″ squares to give you 2.1/2″ half square triangle units. These in turn will give you 2″ finished size squares within the quilt.

### Half square triangle – method two

This method is the one that I use most frequently. You can use chain sewing and make lots of them at a time. Again you need to begin with a pair of 2.7/8″ squares. Place them with right sides together and mark a line along the diagonal. Sew a 1/4″ seam either side of the marked line and cut along the line. You will be left with two triangles each with a seam along the bottom. These open up to form two half square triangles which are 2.1/2″ squares.

Apart from speed, this method also has the advantage that you are sewing the diagonal (bias) edge before you cut it, so you reduce the chance of the fabric stretching along the bias.

### Half square triangle tutorial – method three

In the third method you can make four half square triangles at a time. Cut two 4.1/4″ squares and place them with right sides together. Sew a 1/4″ seam all round the edge of the square. Cut along both diagonals to create four sections. Each one of these will open up to form a half square triangle which is a 2.1/2″ square.

This is a very simple method and I’m not sure why I don’t use it more often.

### Half square triangle tutorial – method four

The fourth method steps the quantity up again – this time you can make eight half square triangles at one go. Cut two 6″ squares and place them with right sides together. Mark a line along both diagonals and sew a 1/4″ seam either side of both of these lines – so that’s four seams that you need to sew.

Cut along each marked line on the two diagonals. In addition, cut the square down the middle both horizontally and vertically.

You will now have cut the squares into eight sections. Each one of these will open up into a half square triangle unit which is 2.1/2″ square.

So there you have it – four methods for making half square triangles. I suspect that I have only scratched the surface here and that there are probably many more methods around, but these ones are all simple to use.

Here’s the video:

I have the Easy Angle ruler, but I find it is a wee bit neat and too small at times. I have now opted for the Magic 8 method, starting with a 6 inch square. I have found that I need to tidy each half-square down to the correct size, but boy is it accurate!

Thanks for those comments. I have never used the Easy Angle ruler and I’m sure other quilters will be interested to hear your view.

Thanks so much for posting all of these techniques together, along with the dimensions! I’ve been looking for notes on dimensions, so these are quite handy.

One observation about the third technique: If the original square pieces of fabric are cut along the fabric grain, the third technique will result in finished pieces whose outer edges are cut along the bias (meaning, if using this method, then handle the finished pieces carefully when piecing and pressing so as not to distort the shape).

Thanks for that comment, Wendy. Very valid point.

Hi Rose – I was wondering, on all of these methods for half square triangles, you say the result will be a 2.5 inch half square triangle square. Is there any wiggle room here? That is, will they need squaring up to be 2.5 inches or do they come out exact every time? Personally, I like a little wiggle room in case I don’t sew an accurate seam. 🙂

Thank you.

Hi Kathleen. The measurements that I have given should give a 2.1/2″ square exactly. I know what you mean about needing wiggle room, but I find that I need to make so many half square triangles that I don’t want to spend extra time trimming. You would need to add a little to all my measurements to give yourself a bit of leeway.