Making Perfect Half Square Triangles!

HST photo
Ah!  The joy of making a perfect Half Square Triangle!

Half Square Triangles are one of my favorite things to make!  If you want to learn how to make the PERFECT HST (or pretty darn close) then you can either watch my video tutorial or read below!  You can also get a cheat sheet emailed to you with all the math on what size to cut your squares, images reminding you where to cut, and all the help you need to make the perfect HSTs.  Get that by clicking HERE.


Watch my video tutorial here:  

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You can also subscribe to my YouTube channel so you can be notified whenever I make a new Quilting Tutorial video!




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Get your CHEET SHEAT here!

Before you start making HSTs, you need to know what size to make them.  Once you know what size to make them, you can refer to my CHEET SHEAT to see what size to cut your squares to begin.

You will also need to decide if you want to make 2, 4, or 8 HSTs at once.  I prefer to make 8 at once, because the more you make at once, the faster it goes.  Plus, I use an amazing RULER that helps me go faster when I make 8 at once.

I will show you with photos how to make 2, 4, or 8 HSTs.

To begin, you will need to draw either 1 or 2 diagonal lines (like an X) on the wrong side of your lightest fabric.  To know if you draw 1 or 2 diagonal lines, refer to the CHEET SHEAT.  I use a ruler and a pencil to do this.


Making 2 HSTs At A Time:

HST4 After making 1 diagonal line on your fabric, pin your 2 fabric squares, right sides together.

IMG_7678 Sew 1/4″ away from the drawn lines on BOTH sides of the drawn line.

HST 20 Cut ON the drawn line.  Finger press your HSTs open, then press them open with an iron, with your seams towards the darker fabric.


Notice these photos are bigger, so you can see the details more clearly.

HST17Using a ruler, place the diagonal line of the ruler on the sewn diagonal line of your HST.  I prefer to use a Creative Grids Ruler.  Find the markings on your ruler where your HST needs to be trimmed to.  For example, in this picture I am squaring up my HST to be 3 1/2″.  You can see the I have found the 3 1/2″ marks on my ruler and lined up my HST with them.  You will notice I did leave a LITTLE extra fabric past the 3 1/2″ marks.  This is intentional, I did that so that I can trim all 4 sides of the square to leave me with a perfectly square HST.

Trim, or square up, the outer 2 sides of you HST.

HST19 Turn your ruler placing the 3 1/2″ markings on the trimmed sides of your HST. (3 1/2″ is just an example here – be sure to use the size you need for you HST).  Then square up or trim the other 2 sides of your HST.  This will leave you with a perfectly squared HST.


HST3 After making 2 diagonal lines on your fabric, pin your 2 fabric squares, right sides together.  Notice the pins are closer to the inside of the square.  This is so you can follow the next step easily, without your pins getting in the way.
HST10 Sew 1/4″ border around the outside of your square.
HST21 Cut ON the drawn lines.

Follow the squaring up steps from above.  


HST2 After making 2 diagonal lines on your fabric, pin your 2 fabric squares, right sides together.  Notice the pins are near the outside of the square, and further away from the drawn lines.  This is to help you avoid sewing over your pins for the next step.
HST13 Sew 1/4″ away from each drawn line on both sides of the drawn lines.
HST15 Cut ON the drawn lines, and then cut vertically and horizontally.
HST16 Before opening my HST and pressing it, I use my Quilt In A Day Ruler to square up my HST.  Using the cheat sheet or the sheet that comes with the ruler, you will know where to place the ruler.
*Notice that for this HST, I am using the 2 1/2″ line as my guide for squaring up.  I place that 2 1/2″ line on the SEWN line, not on the the edge of the triangle.  Keep that in mind if you get your own Quilt In A Day Ruler.

HST17  After squaring up your HST with the ruler, you will need to open your HST and press the seams to the darker fabric.  Then trim those little triangle flaps called Dog Ears.  I place a ruler along the side of my HST while doing this.  I don’t want my rotary cutter slip and accidentally cut my HST!

And there you have it!  The keys that I have found that have made my HSTs turn out pretty darn close to perfect is:
1. Starching my fabric before I even cut my fabric. (See a tutorial here)
2. Using the measurements on my cheat sheet to make sure I have a little extra fabric.  This allows me to square up my HSTs, and when you are able to square up, you are able to get the squares JUST right!
3. When I make 8 HSTs at a time, I will always use the Quilt In A Day Ruler!

If you have any questions or comments, please share them!  I love hearing from you and I am happy to help if I can!

2 thoughts on “Making Perfect Half Square Triangles!”

  1. Thanks for the cheat sheet & tutorials & pics!

    Adding 7/8” though is really difficult on my eyes sometimes even with a good ruler and light. I say life’s too short to waste it on 7/8” lol. I just add 1” instead. We’re trimming them anyways, so that extra 1/8” is no biggie.

    When I square them up, I do it before I press them open. Use the bias line on your ruler. I don’t cut everything off one side, but instead make sure to cut some from both sides of my folded hst. Then I press open a beautifully accurate hst.

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