How to stitch Half Squares triangles for your patchwork blocks

Almost all of the patchwork / quilt blocks consist of squares and half square triangles. These simple shapes can create stunning patterns. Cutting and sewing each of these components individually can seem like a pain, when you have a large project in hand. But it is not rocket science to make these half square triangles in no time.

Half square triangles are square blocks made up of two right-angled triangles. Each triangle in different color or pattern of fabric occupies half of the square’s space.

How to efficiently and accurately create HSTs in various sizes

The obvious way of sewing these half-triangle squares is to cut squares first of both the colors – you will be cutting from two types of fabrics – one a background fabric and another a contrasting colored fabric. Two contrasting fabrics are chosen for visual impact.

Cut the squares 1/2 inch bigger than the final square you want; ie if you want a 3 inch half square triangle cut 2 squares of 3 1/2 inches sides.

Then cut these squares by the middle diagonally. You get 4 triangles. Now join two of the triangles together – making your half square triangle .  

But this is slighlty long winded and there is another easier speedier way. This is to cut your squares after sewing them.

Cut two coloured squares are usual.

Now Keep the two pieces – one dark and one background squares – one on top of the other( Right sides together to the inside.)

Mark a line diagonally as in the picture below along the middle (from one corner to the other)

Sew 1/4 inches to either side of this line – ie you will be sewing diagonally across the block in a straight line on either side of the middle line, from one corner to the other.The line you marked is the cutting line.

Cut along this line.

Separate your triangles.

Press open the seam allowance. Cut the extra corners of the seam allowance projecting outside.

There your 2 half squares triangle are ready with just one stitching. You can many the same way in no time.

A star quilt block is one very easy block that you can make with these half square triangles.

Check out this post on the 9 different types of star patchwork blocks that you can sew with the half square triangles.

The above method will give you two Half Square Triangles per square. But what if you want more in one go and that too easily. There is a hack, ofcourse.

Half square triangles in bulk – 8 HSTs in one go

Step 1. Cut out sqaure fabric pieces as you did earlier, but this time the size will be different.

To calculate the size of the starting squares, take the desired finished size of your HSTs. Double it and add 1 1/4 inch seam allowance

So, intial sqaures to cut = Finished Size of HST×2+1 1/4 inches

Step 2. Place the two squares right sides together. Draw two diagonal lines from corner to corner, creating an X across the square. Draw two lines vertically and horizontally across the square.

Step 3. Sew a ¼ inch seam on both sides of each drawn line along the X.

Step 4. Cut through the lines you have drawn. First, cut vertically and horizontally through the center of the square. Then cut along the two drawn diagonal lines.

In short, the squares are sewn together, cut vertically and horizontally and then along the diagonal to produce 8 HSTs

Here’s a table that shows the initial square sizes you need to cut for various finished sizes of half square triangles (HSTs) using the above method for making 8 HSTs in one go:

Related posts : Different types of quilt blocks ; How to sew a 9 patch quilt block.