QuiltPox.com's Half Square Triangle Tutorial

What are Half Square Triangles?

A Half Square Triangle (known commonly as HST), is a triangle that is half of a square. The long side is on the bias, and the short side on the straights of grain. If you remember your math, this would be the same as a "right square" triangle.

HSTs are a common block to use to create Friendship Star squares, Pin Wheel Squares, and many more. You can just start piecing them from all your scraps and make a very nice scrappy quilt. In it's most simple form, here is a HST square:

Making HST Squares

There are many methods for making HST squares. There are even templates and adhesive paper products for making them quick and fast. I will share my two favorite methods.

Method 1

Perhaps the easisest way to make HST units is simply to take two squares, each 1/2" larger than your desired HST unit, and sew them together, as follows:

  1. Cut two squares of the same size, 1/2" larger than desired finished HST. (Many books recommend using a 3/8" extra, but I find that the 1/2" works better, and you have to square them up anyway.) For example, if you want a 5" finished HST, then you need to cut your two squares at 5 1/2" square.
  2. Draw a diagonal line, going corner to corner, on the back of the *lightest* square.
  3. Stitch a line 1/4" away from the diagonal line.
  4. Turn the square unit around and stitch a 1/4" seam on the other side of the diagonal line.
  5. Press the unit (to set the stitches) and cut the unit into two sections on the diagonal line.
  6. Open each square and press towards the dark fabric.
  7. Using a rotary ruler with a 45° angle, square up the units to your desired size.
Step1 Step2 Step3

Method 2

The method above works fine when you only have to make a few HSTs, but what if you need 100 of these squares? Well, you can do a whole length of them at once.

  1. First, use the HST Calculator to determine how much fabric you need, and how wide to cut your strips: Start HST Calculator Applet
  2. You will need "cut strip width" size from the calculator. Let's assume your strip width is 5.25". Draw a perpindicular line every 5.25" on the wrong side of the lighter of the two fabrics.
  3. Next, draw a diagonal line, corner to corner, from each of the lines you just drew.
  4. Layer the second fabric on top of this right sides together.
  5. Stitch a seam 1/4" away on both sides of the diagonal line as illustrated.
  6. For ease of sewing follow the arrows as indicated on the illustration.
  7. Using rotary cutter and rotary ruler, cut the squares apart on each perpindicular line.
  8. Press each block to set the stitches, then cut on the diagonal line.
  9. Open each HST and press towards the darker.
  10. Trim all HSTs to the desired inch square.
strip method

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