Half-square triangles (HSTs)

Put two squares right sides together, draw a diagonal, sew a quarter inch either side, cut on the line and press. You get two half-square triangle units.

Pinny's tip
Make the units slightly larger than needed and trim them to size afterwards for accuracy.

What you'll need

• Two contrasting fabric squares: cotton.
• Pencil or fabric pen: to draw the diagonal.
• Square ruler: to trim.

Step by step

1. Cut two squares about 1 inch bigger than your finished HST size (or larger, to trim).
2. Draw a diagonal line on the back of the lighter square.
3. Put the squares right sides together and sew a quarter inch either side of the line.
4. Cut on the drawn line.
5. Press the seams, usually towards the darker fabric.
6. Trim each unit to size with the diagonal lined up on the ruler's 45-degree line.

Common mistakes

• Stretching the bias edge. Press, don’t iron.
• Skipping the trim. Blocks won’t line up.
• Drawing on the dark fabric. Lines are hard to see.

Watch it done

• Easy Half Square Triangles Tutorial // The easiest way to make HST quilt blocks for beginners by Homemade Emily Jane (Emily) on YouTube. Opens on YouTube; the video belongs to its creator.
• QUILTING BASICS - Making a perfect Half Square Triangle Block by Just Get it Done Quilts on YouTube. Opens on YouTube; the video belongs to its creator.
• 🌸 How to Make a Half Square Triangle - 4 Easy Ways + Cheat Sheet! by Erica Arndt on YouTube. Opens on YouTube; the video belongs to its creator.

Sources

All checked November 1, 2026. We read these; we did not test the products ourselves.

1. YouTube: Easy Half Square Triangles Tutorial // The easiest way to make HST quilt blocks for beginners (Homemade Emily Jane (Emily))
2. YouTube: QUILTING BASICS - Making a perfect Half Square Triangle Block (Just Get it Done Quilts)
3. YouTube: 🌸 How to Make a Half Square Triangle - 4 Easy Ways + Cheat Sheet! (Erica Arndt)