How to Make Magic 8 Half Square Triangles

If you’ve never learned how to make 8 Half Square Triangles at one time you are missing out! This super magic skill is essential for any quilter, and is even called the Magic 8 HST method! This 8-at-a-time HST technique is a great shortcut for beginners, and is featured in my beginner-friendly Solitaire Quilt Pattern.

You can learn how to make 8 Half Square Triangle Quilt Blocks at one time by reading the step-by-step instructions below, or by watching this quick video:

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Make 8 Half Square Triangles at One Time

Making 8 HSTs with 2 Squares of fabric is a really neat trick! It’s so neat in fact that some people even might call it “Magic”! The Magic 8 Half Square Triangle method is fairly common because of how easy it is!

First, take your 2 squares of fabric and place them right sides together. Draw 2 diagonal on the wrong side of one of the squares using a pencil or an erasable pen like this one.

Stitch lines 1/4″ away from each diagonal line until you have a total of 4 lines sewn making an X across your squares.

Next, press your square of sewn fabric to set the seams. I like to use starch or Best Press here to flatten out any waviness and stiffen up the fabric.

Cut on the diagonal lines that you had drawn previously, and also make 2 additional cuts horizontally and vertically in the exact middle of the square. You’ll be left with 8 triangle-shaped pieces with a seam across the long edge of each one.

Press and trim as desired.

Trimming Half Square Triangles

There are a couple neat rulers that make trimming HSTs a bit easier – and I definitely recommend them! If you like pressing your HSTs to the side, then something like the Block Loc rulers would be perfect for you. If you press open, consider checking out the Clearly Perfect Slotted Trimmers. You can find a demonstration of how to trim them in the video above.

How to Calculate the Beginning Fabric Square Size

Calculating the beginning fabric square size for Magic 8 Half Square Triangles is pretty easy! You begin by figuring out what you want your finished HST block dimensions to be. Take that number and add 1, then multiply by 2. Now you have your starting square size! You’ll need two squares of fabric in that size to make 8 HSTs.

Here is a neat little chart to show what size your 2 fabric squares should be to make your desired finished Half Square Triangle block size. Remember that “finished” means after they are sewn together (so, not including the seam allowance!)