How to make half-square triangles (two at a time)

The building block of hundreds of quilt designs.

Step by step

1. Cut two squares 1 inch larger than the finished size you want (for a 3 inch finished HST, cut 4 inch squares).
2. Draw a diagonal line corner to corner on the back of the lighter square.
3. Place the squares right sides together.
4. Sew 1/4 inch from the line on both sides.
5. Cut on the drawn line. You now have two units.
6. Press, then trim each to the finished size plus 1/2 inch (3.5 inches for a 3 inch finished HST).

Bobbin's tip
Sewing before cutting keeps the stretchy bias edge stable.

Sources

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

1. Janome: HSTs three ways
2. Suzy Quilts: Half square triangles
3. Utah State University Extension: Half square triangles