Half-Square Triangle Math

for designing quilt blocks

Basic Concepts

You can create 2, 4 or 8 half square triangles starting with 2 larger squares of fabric.
  1. Begin with 2 squares of fabric, right-sides facing, same size, and of a different color/pattern.
  2. Draw the solid lines with a fabric-safe pencil.
  3. Sew along the dashed lines, 1/4 an inch from the drawn lines or edges.
  4. Cut along the solid lines using a clear ruler and a rotary blade.
  5. Press the HST units with an iron, trim the dog ears, trim down to size (optional), keeping the 45° angle.
Take out some scraps and practice!


Traditional (2 HSTs) Method

hst2

Quad (4 HSTs) Method

hst4

Octo (8 HSTs) Method

hst8

Calculate Size

The result is rounded down to the nearest 1/16th
All values below are in inches.


Results