How to Sew 32 Half Square Triangles at a Time + HST Size Chart

If you need a whole pile of half square triangles for a quilt, this is such a satisfying way to make them!

Using just two large squares of fabric, you can make 32 matching half square triangles at once, rather than sewing lots of individual pairs.

For this example I’m starting with two 14" squares, which will give me 32 half square triangles measuring 3" unfinished, or 2½" finished once sewn into a quilt.

It’s basically the familiar 8 at a time HST method, multiplied across four sections of fabric.

You will need

For 32 half square triangles:

• Two 14" squares of fabric

• Fabric marker or pencil

• Quilting ruler

• Rotary cutter and cutting mat

• Sewing machine

• Iron

• HST trimming ruler or regular quilting ruler

  
  

Step 1: Layer your fabric

Place your two 14" squares right sides together, lining up all four edges.

On the wrong side of the top square, mark the centre horizontally and vertically at 7".

Draw diagonal lines from corner to corner in both directions.

Step 2: Mark the diagonal lines

Inside each quarter, draw another diagonal line.

You will end up with four X shapes across the large square.

All diagonal lines are your guides for stitching.

Step 3: Sew the HSTs

Keeping the two fabric squares right sides together, sew a ¼" seam on both sides of every diagonal line.

Only sew beside the diagonal lines.

Do not sew along the horizontal and vertical centre lines because these will be cutting lines.

Pinning the layers in a few places can help stop such a large piece of fabric from shifting while you sew.

Step 4: Cut the large square into four

Once everything is sewn, cut directly along the horizontal and vertical centre lines.

Your 14" square will now be divided into four 7" squares.

Each of these is essentially an 8 at a time HST unit.

Step 5: Cut each section

Working with one 7" square at a time, make four cuts:

• Cut vertically through the centre

• Cut horizontally through the centre

• Cut along one marked diagonal

• Cut along the other marked diagonal

Repeat for all four sections.

Step 6: Press and trim

Open each HST and press the seam.

You can press the seam to one side or press it open depending on how you prefer to piece your quilts.

Trim each HST to 3" square.

Once sewn into your quilt using a ¼" seam allowance, each HST will finish at 2½" square.

And just like that, you have 32 matching HSTs ready to use.

One of my favourite things about making 32 half square triangles at once is that you have enough to make two 4 x 4 quilt blocks, using 16 HSTs in each block.

From the same batch of HSTs, you can create so many different designs just by turning the units in different directions.

You could make:

• stars

• pinwheels

• chevrons

• diamonds

• zigzags

• geometric crosses

• flying geese style layouts

  
  

Try laying all 16 HSTs out in a 4 x 4 grid before sewing anything together, then rotate individual units until you find a design you like.

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32 at a Time Half Square Triangle Size Chart

The sizing method commonly used for 32 at a time HSTs is:

Starting square = ((unfinished HST size × 2) + 1") × 2

Or, a little more simply:

Starting square = unfinished HST size × 4 + 2"

Remember: the unfinished measurement is the size of the HST before it is sewn into your project. It will finish ½" smaller after the ¼" seam allowances are used.

What can you make with 32 HSTs?

This is where half square triangles become really fun because exactly the same 32 units can be rearranged into completely different designs.

Try using them for:

• Sawtooth stars or other star quilt blocks

• Pinwheels

• Flying geese style arrangements

• Chevron or zigzag designs

• Diamonds

• Hourglass inspired layouts

• Borders around a quilt

• Patchwork cushions

• Table runners

• Quilted bags

• Sampler quilts

  
  

You could also make several batches using different fabric combinations, then mix all of your HSTs together for a more scrappy quilt.

This method is particularly useful when a quilt needs lots of the same two fabric combinations. Instead of repeatedly cutting, marking and sewing small squares, most of the work is done in one go.

Save this method for your next HST quilt

Two 14" fabric squares.

A little marking and sewing.

And 32 half square triangles ready to become something lovely.

Once you know the method, it’s an easy one to scale up or down using the chart above, and definitely one worth keeping in your patchwork toolkit!

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Find your next project

If you’re looking for your next project, you can find more of my quilt patterns and sewing patterns in the shop. I’ve got everything from simple patchwork projects to larger quilts, with step-by-step instructions to help you turn all that quilt block practice into something finished. Browse the sewing patterns here →

Happy sewing! Kym