The Half Square Triangle: A Versatile Quilt Block

Half Square Triangles, or HSTs for short, are one of the most versatile quilt blocks to make. Not only are they commonly found as smaller units within a block, but you can make an entire quilt out of nothing but half square triangles, in several different layouts.

HSTs are fairly straight forward when it comes to construction, and like many blocks in quilting, can be made several different ways. Before you learn how to make them, it’s important to know the difference between a ‘finished’ measurement and an ‘unfinished’ measurement, as these terms are used when determining what size of fabric square to start with in order to make the desired size of half square triangle. A ‘finished’ measurement refers to what size the block will be once it is sewn into a quilt. An ‘unfinished’ measurement refers to what size the block is before it is sewn into a quilt- meaning that it takes into account the ¼” seam allowance.

The first, and probably most common way to make an HST is to start with two squares of contrasting colored fabric. On the wrong side of one of the fabrics, draw a diagonal line from corner to corner. Align your fabric squares with right sides together and pin. Stitch ¼” on either side of the drawn line and then cut apart on the line.

Open up the half square triangles and press. This method will yield two half square triangles at one time. If you are wanting to make a specific size of HST, the way to figure out what size square to start with is to add 7/8”. For example, if you want to make an HST that finishes at 3”, you would start with two 3 7/8” squares.

If you are making an entire quilt from nothing by HSTs, or are just wanting to make more of them at a time, you can use an alternative method that allows you to make eight half square triangles at one time. Begin with two contrasting colored fabric squares. On the wrong side of one of the fabrics, draw two diagonal lines from corner to corner. Align the fabric squares with right sides together and pin. Stitch ¼” on either side of the drawn lines. Cut apart along the center vertically and horizontally and then along each of the drawn lines.

Open up the half square triangles and press. If you are wanting to make a specific size of HST, begin with the finished HST size. To that size, add 7/8” and then multiply by 2. For example, if you want to make HSTs that finish at 3”, you would start with two 7 ¾” squares. ((3 +7/8) x2). If your math does not yield an easy measurement, you can always round up to make slightly larger HSTs and then square your HST down to the correct size once it is pressed open.

Now you can try out these fun blocks to practice your HST skills:

Pinwheel and Broken Dishes

Make four HSTs and lay them out as shown. Sew together into two rows of two, and then sew the rows together.

DOWNLOAD PINWHEEL PDF 1

DOWNLOAD PINWHEEL PDF 2

Both Pinwheel blocks and Broken Dishes Blocks are made from the same number of HSTs, the only difference is how you lay them out.

DOWNLOAD BROKEN DISHES PDF 1

DOWNLOAD BROKEN DISHES PDF 2

If you want to make a lot of HSTs and put them together into a quilt, try out any of these fun layouts. All are made from HSTs in two colors- the only difference is how they are arranged. Simply layout the blocks as shown, sew together into rows and then sew the rows together. We’ve compiled 9 different layout ideas, for you, but the possibilities are endless! Make sure to show us what you come up within our National Quilters Circle Community Gallery!

Have something to add? Leave a comment or email editor@nationalquilterscircle.com.

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3 Responses to “The Half Square Triangle: A Versatile Quilt Block”
  1. Martha

    Are there instructions that i can purchase for each of the layout options given here?

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    • Customer Service

      Hello Martha,

      Thank you for contacting us. I’m sorry but there are no printed instructions to purchase, but you can print these out for yourself to keep in

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