The Only Half Square Triangle Chart You Will EVER Need!
Have you ever gone to look up how to figure out what size squares you need to make half square triangles and ended up being utterly confused and frustrated? Ugh, I know I have, and that’s not a fun feeling. Today, I want to break down half square triangle math so it’s easily understandable, and you can feel confident the next time you need to do some quick math for HST quilt blocks.
I will show you how to make HSTs using the two at a time, four at a time, and eight at a time methods. You’ll learn the math behind the method for those quilt nerds like me. I’ll also include a half square triangle chart with how-tos and measurement cheat sheets for each method.
How To Calculate Half Square Triangles
If you’re not into math and prefer to use a handy dandy cheat sheet, I’ve included a half square triangle chart for each method for HSTs ranging from 3” to 12”.
For my fellow nerds, let’s take a deep dive into each HST method and learn the math to make HST blocks easily. I also include diagrams for each method showing you step-by-step how to make half square triangle blocks for each method.
If you want all diagrams in this blog post, you can click the link below to download a printable PDF.
How to Make Two HSTs at a Time
This is an excellent method when you just need a couple of HSTs and want zero-waste quilt blocks. The two HST at a time method has the most straightforward math equation. Are you ready for it?
The Equation
Finished HST block size + 1”= Starting Square Size
Pretty easy, right? So, for example, if I want 4” finished HST quilt blocks, I would add 1” to that number to get 5”. That means I start with two 5” squares to make my HSTs.
Follow the diagram below to make two HSTs at a time.
As you can see, constructing two HSTs at a time is simple to achieve. Below you will find a half square triangle cheat sheet for this method, concluding the two at a time method!
Half Square Triangle Cheat Sheet: Two at a Time Method
How to Make Four HSTs at a Time
Making four HSTs is another fantastic option, and is a fun process, so let’s jump right into it!
Note: It’s important to note that there is one downside to making four HSTs at a time: when you cut the HSTs from the square, you will be cutting on bias edge seams. This is significant because those seams will be extra stretchy since they’re on the bias, so if you choose this method, be careful not to tug or pull the fabric when cutting to avoid any stretched or wonky seams.
The Equation
- Finished HST block size + ½”= Unfinished HST block size
- Unfinished HST block size ÷ .64= Starting Square Size
For example, if I want a finished 4” HST quilt block, I will first add ½”. This gives me 4 ½”. I then divide 4 ½ by .64, which gives me 7.03125. I always round up to the nearest ¼” just to be safe. In this case, I round the number 7.25” (7 ¼”.) You can always trim the blocks to the correct unfinished size. So to make four 4” HSTs at a time, I need to start with two 7 ¼” squares.
Follow the diagram below to make four HSTs at a time.
After you cut all four HSTs from the larger squares, press the seam to one side and trim them down to the required unfinished size. Pretty fun, right? And the math isn’t too bad! Don’t worry; I made a cheat sheet for this method as well that you can reference down below.
Half Square Triangle Cheat Sheet: Four at a Time Method
How to Make Eight HSTs at a Time
Have you encountered a quilt pattern that uses A LOT of HSTs, and you want to cut down on production time? This method is the perfect choice for you! The math is surprisingly simple too, which is always a bonus!
This is my personal favorite method and will be featured in the new FREE quilt pattern that I will be releasing in a few short weeks!
The Equation
(Finished HST block size x 2) + 2= Starting Square Size
For example, if I want a finished 4” HST block, I need to multiply 4 by 2, which gives me 8. Then I add 2 to get 10”. My starting two squares need to be 10”. Not bad at all!
Follow the diagram below to make eight HSTs at a time.
Now let’s review the half square triangle size chart for the eight at a time method.
Half Square Triangle Cheat Sheet: Eight at a Time Method
My Favorite Half Square Triangle Tools
In this section, I will list out all of the tools that help me make perfect half square triangle quilt blocks every time. Some of the links are a part of the Amazon Associates Affiliate program. If you use any of my links, there is no extra charge to you, but I may receive a small percentage of the sale. This money allows me to provide free content for all of you, and I truly appreciate all of your support!
- Rotary Cutter
- Marking Pen
- Omnigrid Square Rulers
- Creative Grids 4-in-1 HST Ruler
- Juki TL-2010Q Sewing Machine
Wrap It Up!
I hope the equations and diagrams in this post will help you feel more confident when making half square triangle blocks for your next quilt project. A half square triangle chart is extremely helpful, so feel free to use the free cheat sheets any time.
If you have problems downloading them, please feel free to email me at miriam@stitchobsessed.com
Thank you so much for stopping by, and Happy Stitches!
Thank you so much for all of this. I was checking out my file “quilting charts” and realized I didn’t have one for hst’s . This covers them all and it’s downloadable. Thanks again!
Of course! I hope you enjoy it! It’s quite handy haha!
thank you so much for this chart. I have an interesting quilt with all half square triangle that I want to try with different sized blocks and this is a life saver.
You are so welcome! I hope you enjoy the chart and have fun making lots of HSTs!