top of page

How to...Half Square Triangles

Half square triangles are a patchwork staple.

There are a few ways to make half square triangles (HSTs). I am going to show you a technique that is good for beginners, that doesn't involve having any stretchy, bias edges on the sides of your square.

To make a 3 1/2" HST you will need two contrasting squares measuring 3 7/8"

On the wrong side of one of the squares (usually the lightest colour) draw a line diagonally from one corner to the opposite corner.

Place the 1/4" line of your ruler on the line you have just drawn and draw a second line.

Repeat to draw a third line on the other side of the first line you drew.

Place your squares right sides together and pin.

Stitch along the outer lines, either on the line or just inside it (my stitched line is just inside the pencil line rather than on it).

Cut the square in half along the centre line.

Press the seams open or to the dark side (my preference is open so I can see where to match and stitch the points when they are stitched together).

Check the size of your HSTs by using the 45 degree line on your ruler to line up with the seam line. Trim off any excess and turn your square to trim the other sides.

If you are making lots of HSTs find the smallest ones and trim all your HSTs to this size. I have found that stitching just inside the line helps with accuracy.

For different size HSTs, add 3/8" to the size of the unfinished square you want. E.g. if you need a 2 1/2" unfinished HST cut your starting squares to 2 7/8", for a 4" unfinished square cut you starting squares to 4 3/8".

Let us know how you get on in the comments.

Happy stitching!


bottom of page