How to Make
Individual Half Square Triangles

Technique #2 - Creating a HST plus a bonus unit

Make a half square triangle plus a bonus

Half square triangles are one of the standard units for patchwork piecing.

Quilting books also refer to them as a triangle squares or abbreviate it as 'HST'.

This unit is a square made from two equal right triangles.

The diagonal seam through the middle is on the bias while the outside edges are all of the straight of grain for stability.

Create a Half Square Triangle Plus...
a Bonus Unit from Squares

For this technique, you'll sew two squares together with one seam and create a single triangle square unit.

Pros:

Method creates a single triangle square unit
No 'magic numbers' to remember
No special templates, tools or triangle paper needed
Cut from the same size strips as other patches are
Adding a second seam creates a bonus HST to be used later

Cons:

If you don't intend to use the 'bonus' triangle, there's a lot of waste
Each patch is individually marked
There are faster methods for creating multiple identical units

Now, let's get started!

The Technique

The Formula

Cut two squares equal to the finished size plus 1/2" for seam allowances.

Step 1

In this example, we want a 3-1/2" finished HST unit, so we cut two squares 3-1/2" plus 1/2" or 4" x 4".

Step 2

Mark a diagonal line from corner to corner on the back of the lightest square. This line need only be as dark as you need to see it. Take care not to 'pull' on the bias with your pencil. (I've used the Bohin Mechanical Chalk pencil in white in the picture below. This chalk pencil is my first choice for a marking tool because it produces a consistently fine line.

Step 3

Layer the two patches right sides together, aligning all the edges. Stitch on the line from corner to corner.

Sew the half square triangle diagonally from corner to corner

Step 4

If you're a scrap quilter, then stitch a parallel line, 1/2" from the first. This creates the 'bonus' triangle with enough fabric for seam allowances for both units.

Note the scrap piece of fabric. Sometimes your sewing machine wants to 'eat' the points of these squares. To eliminate this problem start by sewing onto a scrap first and then onto your squares. I call this scrap a 'spider', others call it a 'bunny tail' or anchor cloth. I'm sure there are more names...

It also helps to starch your quilt fabric before stitching.

Stitch a second line to create a bonus half square triangle

Step 5

Press the unit flat to set the seam.

Step 6

Cut the sewn squares in two between the stitching lines.

If you chose not to create a bonus unit, then trim away the excess fabric 1/4" from the stitching line on one side.

Step 7

Finger press along the seam line to minimize the chance of a tuck forming. Press flat with your iron and trim off the dog ears. The dog ears have been trimmed from the larger triangle square (below, left), but not from the smaller, bonus unit (below, right).

Press the half square triangles open and remove the dog ears

The final triangle unit is 4" unfinished (the same size as the cut squares because you stitched down the center diagonal) or 3-1/2" finished. The bonus unit is approximately 3-1/4".

Admittedly, at some point, the bonus triangles just get too small.

But with larger half square triangles, you end up with a nice bonus unit with little extra work. Keep them neatly stored and trim just before using in your next scrap quilt.