How to Make Half-Square Triangles (HSTs): 3 Easy Methods for Quilters
If you’re a new quilter, chances are you’ve run into half-square triangles (HSTs) already—and if you haven’t, you will soon! HSTs are one of the most versatile and beginner-friendly blocks in quilting. From pinwheels to chevrons, they show up in all sorts of classic and modern designs.
Today, I’m breaking down three simple methods to make half-square triangle units, along with formulas for choosing the right starting square sizes. Let’s stitch!
What is a Half-Square Triangle?
A half-square triangle is a square made up of two equal right-angle triangles, divided along the diagonal. They’re simple in construction but full of design possibilities.
Now let’s get into the good stuff—how to make them!
Method 1: Two at a Time (Quick & Simple)
This is the most common way to make HSTs, especially if you only need a few for your project.
How to:
Place two squares right sides together.
Draw a diagonal line from corner to corner.
Sew ¼" away from both sides of the line.
Cut along the drawn line to make two HSTs.
Press and trim to your desired unfinished size.
Formula:
Starting square size = Finished HST size + 1 inch
💡 Example:
Want a 4" finished HST?
Start with two 5" squares (4 + 1 = 5)
Download the Half Square Triangle Cheat Sheet HERE!
Method 2: Four at a Time (No Marking Needed!)
If you want to speed things up a bit and avoid drawing lines, the four-at-a-time method is for you.
How to:
Place two fabric squares right sides together.
Sew ¼" around all four sides of the square.
Cut the sewn square diagonally in both directions (like an X).
Press open and trim as needed.
Formula:
Starting square size = Unfinished HST size ÷ 0.64
Then round up to the nearest ¼" for accuracy.
💡 Example:
Want a 4½" unfinished HST?
4.5 ÷ 0.64 = 7.03 → Round to 7¼"
Start with two 7¼" squares
Download the Half Square Triangle Cheat Sheet HERE!
Method 3: Eight at a Time (Batch Maker’s Favorite)
Need a lot of HSTs in a hurry? This method lets you make eight at once!
How to:
Place two squares right sides together.
Draw two diagonal lines from corner to corner, forming an X.
Sew ¼" on both sides of both diagonal lines.
Cut the square horizontally, vertically, and along both diagonals—you’ll end up with 8 triangles.
Press and trim.
Formula:
Starting square size = (Finished HST size × 2) + 2 inches
💡 Example:
Want 3" finished HSTs?
(3 × 2) + 2 = 8
Start with two 8" squares
Final Thoughts
Each method has its place in your quilting toolbox. Use the 2-at-a-time for smaller projects, the 4-at-a-time when you want a fast, no-marking option, and the 8-at-a-time for those big quilts that call for dozens of HSTs.
And remember—no matter the method, a little extra trimming makes your blocks shine! ✨
Have a favorite way to make your HSTs? I’d love to hear in the comments or over on Instagram @StraightStitching. Happy stitching, friends! 💛
