Quilting How-To Half Square Triangle Four at a Time Method  

The half square triangle is a building block for many more complex blocks.  It can also be used in borders and by itself to make many amazing designs.

One of my favorite way to make half square triangles makes four at a time.

  • Cut 1 square of fabric for each of the two colors used in the half square triangle.  One purple and one white in this example.
  • Determine the minimum size of the squares by using the MyWebQuilter Half Square Triangle Calculator

  • Cutting your squares a little larger than the minumum makes everything easier and allows you to be more accurate. I usually round up to the next half or whole inch.

  • Stack the two square right sides together

  • Sew a 1/4 inch seam around the edge

  • Cut diagonally in both directions to create 4 half square triangles.  Press seam toward the darker fabric or press the seam open.


  • Square up the patches to the finished size plus 1/2. For example for a 6 inch finished square trim to 6 1/2 inches.

  • To square up the block, use a ruler with a 45 degree line.  Align the 45 degree line with the diagonal seam on the block. Trim the edges to the proper size. 

  • If you made the starting squares a little oversized, there will be more waste at this point.  However, there is less chance that the half square triangle will be too small!


  • With this approach, the sides of the blocks are on the bias and may be prone to stretching.  Press carefully to avoid stretching the blocks.  Using spray starch may be helpful.