Calculations for Half Square Triangles

Question

I am making half square triangles from squares cut 2-7/8".


What is the size of the triangles after being sewn. (i.e. like for square patches when the cut size is 2-1/2" and the finished size is 2")

Reply

You'll make two half square triangle units from two squares of fabric cut 2-7/8".

Draw a line diagonally from corner to corner and then stitch a quarter inch away from both sides of the drawn line. This will give you two triangle squares that finish 2" square or 2-1/2" unfinished. So every time you use this technique, just add 7/8 inch to the finished size and cut two squares of fabric.

This method is shown in detail at Creating Half Square Triangles - Technique #1.

Different Technique, Different Finished Size

Now if you use the same two 2-7/8" squares and sew diagonally from corner to corner, you will create only one unit that measures 2-7/8" unfinished or 2-3/8" finished. Every time you use this technique, just add 1/2" to the finished size and cut two squares of quilt fabric. You may choose to make an additional 'bonus' unit from the waste, but it will always be smaller then the original.

This method is shown at Creating Half Square Triangles - Technique #2.

I will be other methods for creating triangle squares. The starting measurements will differ depending on the technique.

Thank you for your question.

Piecefully,

Julie Baird
Editor