Wednesday, May 27, 2020

Half Square Triangles - 4 at a Time!

Two squares of fabric = 4 half square triangles. This easy method is a great way to make several HST's at once. 
There are several ways to make them. Previously, I've shared the traditional HST method, and the 8 at a time method.  

Today we'll cover how to make 4 at a time. 

PLUS get a free printable cut list cheat sheet! 

four red and white half square triangles

Half square triangles are a foundational unit in piece quilting. They are used in a variety of ways. Many quilt blocks use HST's, including the Jacob's Ladder, Shoo Fly, and Birds in the Air.

These particular HST's were used in a Churn Dash block.


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image with squares of fabric and 4 half square triangles
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The formula for making these HST's is a little tricky and it's not exact. 

Begin with the trimmed size of HST that you want. This will include the seam allowance. 

So if you would like a final size of 3 inches the trimmed size will be 3 1/2 inches.  

Take the trimmed size and divide it by .64     3.5 ÷ .64 = 5.47 

Now add 1/4 inch.  5.47 + .25 = 5.71

Now round up to the nearest quarter or eighth of an inch to make it easier = 5.75 or 5 3/4 inches.

Don't worry about doing all the math. I've done it for you for the most common square sizes.

If you want your own printable chart for easy reference be sure to scroll to the end of the post. Sign up and it will be sent directly to your email.

My method is slightly different than most because I add the quarter inch. I played around with several sized HST's just dividing by .64.

The results varied. Some sizes were exactly on. Some were too large and some were too small. 

I decided that by adding 1/4 inch and then squaring up after they're made gave me much better results.

HOW TO MAKE HST's - 4 at a time.

Begin by determining the size of fabric needed. Use the chart above to help with this.

cut out two squares of fabric

Cut two squares of fabric. Place them so that the right sides are together.

sew the two squares together around all four sides

Sew the two squares together with a 1/4 inch seam allowance. Sew around all four sides of the square.

image depicting cuts through fabric diagonally from corner to corner in both directions

Using a straight edge, cut diagonally from corner to corner in both directions.

Open up the fabric and press the seam toward the darker color.

squaring up a half square triangle

Square up the triangle to the exact size needed.

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Don't forget to pin it!!

image of 4 HST'simage of 4 half square triangles


  1. Thanks for these tips. Getting ready to work on a quilt with lots of hst. but i noticed in the chart you show the formula as: Trimmed size x .64 + 1/4 inch. Shouldn't it be divided by .64?

    1. You are correct, I will get that corrected! Thanks!

  2. You can size up your HST in half the time if you size them BEFORE you iron them. Use your HST square up ruler or mark a regular ruler
    with tape. Mark (for instance) 2 1/2" up both sides of the corner of your ruler then place the edge of your painter tape across the corner of
    your ruler connecting the 2 1/2" mark Place the sewed line on your HST on the edge of the tape representing
    the 2 1/2" finished HST and cut along both ends of your ruler. (or square up ruler.) you have cut both sides at the same time.