Multiple Half Square Triangle Tutorial

Hello Everyone! Today we are going to make multiple Half Square Triangles at a time, any size you need. In the upcoming Needles projects that I designed for Jacquelynne Steves’ Art of Home Club, I needed to make a lot of HSTs out of the same fabric, which I don’t usually do. For one of the designs, I needed to make 16 2″ finished HSTs and I wanted to use a 10″ layer cake square.
IMG_6716.1I already knew how  to make 8 HSTs from a square, but that formula didn’t work for what I was trying to do. I searched the internet and never came up with exactly what I wanted, but I did find this YouTube video by Amy Smart that came close to what I wanted to do. She was making 16 4″ finished HSTs. Her tutorial is very specific to what she was making, so I watched a few times, played around with different layouts and finally figured out a formula to use on any size HST.

I’m going to go through the steps for making 18 2″ finished HSTs using two 10″ squares, then at the end, I’ll give you the formula for making any size. I’ve added Making Multiple Half Square Triangles Tutorial  to my Tutorial Page for easy reference and printing.

Draw Lines and Sew

Take two 10” squares and put right sides together with the lighter side up.

Drawing Lines

  1. Draw (9) 3” squares (outlined in blue).
  2. Draw a diagonal line through each square as shown above (the dashed line).
  3. Draw a 1/4” line on each side of the dashed line.
  4. Draw the arrows and numbers as shown for the sewing path.
  5. Sew along the solid lines, starting at start and following the arrows to the end.

Sewing Direction

Sew through the intersections as shown.

Seams Crossing

Cutting and Pressing

When cutting, do not pick up your pieces. Use a rotating mat if you have one.


  1.  Cut all the vertical solid lines (the 3” square outlines)
  2.  Next, cut the horizontal solid lines.
  3. Cut the diagonal lines last, cutting on the dashed lines as shown above.

Pressing and Trimming

The triangles will be slightly oversized so they can be trimmed to the exact size.

  1. Press each seam towards the darker fabric.
  2. Using a ruler with a diagonal line, place the diagonal line on the seamline as shown in Fig. 1, leaving a little extra fabric around each edge.
  3. Make the first cut along the right and top edges, see Fig. 2. Note: If you are left handed, the first cut will be along the left and top edges.
  4. Turn your mat or the square and place the 2 1/2” lines on the previously cut lines.
  5. Trim the right and top edges for this side of the square. (Fig. 3)
  6. Now you have a perfectly squared Half Square Triangle unit. (Fig. 4)

Formula For Making HSTs

Unfinished size + 1/2″ = drawn box size

For example, if you want to make 3″ finished HSTs, take the unfinished size,

3 1/2″ + 1/2″ = 4″.

Draw your box size on your fabric 4″ x 4″. 

Rough SketchI used this very rough sketch to draw out boxes to make 20 3″ finished HSTs (3 1/2″ unfinished) on two fat eighths ( 9″ x 21″). I needed two pieces of fabric that were slightly larger than 20″ x 8″. I used the rough drawing as a visual guide to draw the sewing and cutting lines. After cutting, I trimmed the pieces to 3 1/2″ unfinished.

IMG_6598.1Here are a few of the 3″ HSTs in the Needles Wall Hanging.

I hope you find this tutorial helpful when you need to make multiple HSTs from the same fabric. You can always use triangle paper, too, but for me, I didn’t want to buy paper that would fit my 10″ square when I only needed 16 squares.

Thanks for stopping by and I’ll be able to show the Needles projects on Monday!






This entry was posted in New Techniques, Tutorials, Uncategorized and tagged , . Bookmark the permalink.

3 Responses to Multiple Half Square Triangle Tutorial

  1. Patricia Cash says:

    Thank you, can’t wait to try this. i have messed up too many half square triangles.


  2. Lydia says:

    I think you are going to have to come over here and hold my hand while I do this one!


  3. Pingback: The Needles Projects for the Art of Home Club | The Quilting Nook

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