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Make Pinwheel Quilt Blocks from Half Square Triangle Units
Pinwheel Quilt Block

Assembling a Pinwheel Block

© Janet Wickell


There are several ways to make half square triangle units -- sometimes called triangles squares. Cutting and piecing individual triangles is perhaps the slowest and least accurate method. Quick piecing is a good choice because it helps you put these popular quilting units together quickly and accurately.


I like to make half square triangles from sandwiched squares of fabric that are sewn together twice along their diagonal, then cut apart to yield two units.

  1. Cut two 4-7/8" dark squares and two 4-7/8" light squares.
  2. Follow my easy instructions to make four half-square triangle units from the squares. When complete, the units should measure 4-1/2" square.

I nearly always begin with oversized squares, then trim my sewn units back to the correct size with a square ruler that has a 45-degree line along its center to help me ensure that each triangle takes up exactly half of a square's space (instructions are included in the linked tutorial).

Triangle Squares on a Grid

Use the long grid method to make four half square triangle units. Your fabric strip should be 4-7/8" wide.

Commercial products of all sorts are available, too, and so are special rulers to help you make triangles squares from long strips of fabric.

Assemble the Pinwheel Block

Use Quarter Inch Seams Throughout

  1. Arrange the completed 4-1/2" half square triangle units into two rows as shown above. Press seam allowances towards the darker triangles.
  2. Sew the rows together, matching edges and midpoints carefully. Press the new seam allowance either direction.
  3. Check your block. It should measure 8-1/2" square.
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