Split Half-Square Triangles: Paper Piecing

blue and white split half square triangle with title.

Paper piecing will give you accurate results for split half square triangles every time. It takes a bit of time to do, but the perfect results are worth it.

You can purchase pre-printed papers for the piecing, but if you only need a few it is easy to just make your own. Any kind of paper will work, but if you have graph paper with an accurate 1/4″ spacing, it is even easier.

Draw the split half square triangle shape on the paper in the exact size you want the finished piece to be. This sample will be 3″ square and it is on 1/4″ graph paper.

If you need help to remember about the seam allowance, draw another larger square 1/4″ away from the outer line.

split half square triangle paper drawing.

Roughly cut triangles that are larger than the shapes on the paper. Remember, it is easier to trim down later than to fix it if you come up short.

fabric triangles for paper piecing.

Place the two smaller triangle pieces right sides together and pin to the back of the paper under one of the small triangles.

Holding the piece to the light will help you see that they are aligned. Remember you need 1/4″ seam allowance around the triangle, so you need to be past the lines.

aligning fabric triangles with paper.

Stitch directly on the seam line between the smaller two triangles.

stitching seam on paper.

Trim the seam to 1/4″, open and press.

first two triangles for split half square triangle units.

Lay the larger triangle right side onto the smaller triangles and stitch along the centre seam line.

stitching second seam on paper.

Open and press.

pressed split half square triangle.

Trim the finished piece. Don’t forget you need a 1/4″ seam allowance!

trimmed split hst unit.

Gently remove the paper from the back.

removing paper from stitched unit.

Some people love paper piecing and some people hate it, but even if you normally hate it, you might find it works for this piece.

What’s Good

  • simple to stitch
  • very accurate
  • easy to make odd sizes

What’s not Good

  • time consuming
  • paper is one-time use
  • difficult to chain piece

When to use this method

  • when you need very accurate pieces

Rating: 4 out of 5

This method is good to use when you need the pieces to be exactly accurate. It works with any size, and you can even use oddly shaped triangles. They don’t have to be right angle triangles.


flying geese unit with title.
blue and white fabric pieced triangles with title "half square triangles".

Elizabeth DeCroos - Epida Studio.

Elizabeth DeCroos

Elizabeth DeCroos is the designer and teacher at Epida Studio. She loves to work in quilting, pojagi and embroidery and teach these techniques to others.
Learn more and get her to speak to your group.

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