This is a quick method to use when you need a bunch of half square triangles (HSTs) – 8 at a time! Of course all 8 come out identical, so if you’re doing any kind of project where you want 8 matching HSTs, this is the best way! But also if you are doing a scrappy quilt with quite a few HSTs, you could still use this method – just make sure to spread out the identical HSTs throughout your quilt.
At the end of this tutorial, and also under the “downloads” tab on my website, you’ll find a pdf with a chart listing the size of the beginning square needed to yield any given size finished HST. I’ll go over the chart in more detail at the end.
Start with two squares according to the chart
Cut two squares according to the chart. Place them right sides together (RST). Using a fabric marking pen and a ruler, draw a line on both diagonals. Place a pin or two if you like – I usually do, somewhere away from the drawn lines.
Sew a 1/4″ away on both sides from the drawn lines.
You end up with four stitching lines.
Cut apart through both diagonals and both horizontally and vertically
Now cut the block apart between the seams along the drawn line. Then again, through the center, both horizontally and vertically. I have a small cutting mat I use for this step. I can make cuts in one direction, then rotate the mat without disturbing the block, and make cuts in another direction. In this way, I can get all four cuts done quickly and accurately. And here you have all 8 HSTs!
Trim the HSTs – two methods
Let’s trim up the HSTs to the correct size. At this point, remember to trim to the unfinished size. I most often use a ruler called the Clearly Perfect Slotted Trimmer, which makes trimming so easy (no I’m not getting paid for this recommendation.) You can see this ruler in the photo above left. One of the best parts of this ruler is that you trim before you iron the HST open. Line up the marking with the unfinished size along the stitching line, (in my case 4 1/2″) then trim both sides of the triangle. Also at the bottom corners are slots you can use to trim the dog ears – I’ve used this ruler so much I usually just eye ball that cut. Once trimmed, press open.
Of course if you don’t have this trimmer, you can use a regular quilting ruler. You can see this in the photo above right. Press the HST open (usually towards the darker fabric if there is one) and line up the diagonal ruler line along the diagonal on the HST. Also line up the ruler at the marking for the unfinished size (in my case 4 1/2″) then trim the right and top edges. Turn the HST and trim the other two edges in the same way.
HST layout ideas
Below are just a few HST layouts – what a versatile block the humble HST is! And now you know how to make 8 at a time 🙂
Free Downloadable Size Chart
Below is a chart to work out what size beginning square you need to yield any given size HST. The formula is also listed in case you need a size not listed.