Half square triangle blocks are one of first non-square patterns that new quilters typically explore. As you become a more experienced quilter, you gather tricks for making half square triangles easier along the way! In this post, I’m sharing 15+ free half square triangle blocks and quilt patterns from my favorite designers, along with tips and tools for getting perfect half square triangles every time.
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If you’re new to half square triangles, I’ll start by going through the basics, and then show you some of my favorite tips and tools for making perfect half square triangles. Finally, I’ll share 15+ free patterns for half square triangle blocks and quilts to get you inspired to sew!
Half Square Triangles: The Basics
What are half square triangles (HSTs)?
Half square triangles, also known as HSTs, are foundational to so many traditional and modern quilt patterns that most new quilters are eager to learn how to make them. As the name suggests, these are triangles formed from dividing a square in half along the diagonal from point to point. HST blocks include two right triangles (that are also isosceles triangles with two equal sides) joined together to form a square. Many well known quilt block patterns — including the Pinwheel, Broken Dishes, Flower Basket, Friendship Star, Churn Dash, Churn Dash, and Shoo Fly — rely on half square triangles.
How To Make a Half Square Triangle Block
When I first saw half square triangles, I thought: “That looks too fussy for me.” I imagined cutting out a bunch of triangles and then sewing them together at the long edge. If you like taking your time with learning a new method, or if you have a lot of scrappy triangle pieces in your collection, this could be the right approach for you. But, there are also several (easier, in my opinion!) ways to make multiple half square triangle blocks at the same time!
To easily make two HST blocks at once, position two square pieces of fabric with the right sides together. Mark the diagonal line on the wrong side of one of the squares. Join the two squares with a 1/4″ seam on one side of the marked line. Then, repeat with a 1/4″ seam on the other side of the marked line. Using your rotary cutter and ruler or sharp fabric shears, cut the marking line. Press the seam on each half square triangle block.
Want to know how to make four HST blocks at once? Check out this tutorial from Adventures of a DIY Mom. It includes both photo and video tutorials, and a cutting chart for different size blocks.
Need to know how to make eight HST blocks at once? Check out the video below from Teresa Down Under.
How about making 16 HST blocks at once? The video below from Diary of a Quilter will show you how!
You can even use foundation paper piecing to make half square triangles, as shown in this tutorial on Gathered.
Half Square Triangles: Tools
Now that you know six different ways to make half square triangles, here are tools that make the entire half square triangle process much easier. First, you’ll need all the basics like a sharp rotary cutter and a cutting mat, pins, and a good fabric pencil or marker. Here are some other tools that you may find helpful.
The Clover No-Hassle Triangle Gauge is an easy-to-use tool for making half and quarter square triangles in five sizes from 2-1/2″ to 6-1/2″ blocks. It tells you what size squares to cut for the two HST blocks at once method shown above, and then has a sliding gauge with a slit in the center to help you mark the blocks for sewing. This video from Clover shows you how it works.
Several companies make special acrylic rulers to use with your rotary cutter and cutting mat for perfect half square triangles.
- Bloc_Loc, Clearly Perfect, Creative Grids, Deb Tucker, Omingrid, Quilt in a Day have square up rulers to help you square up your finished HST blocks in a variety of sizes.
- Creative Grids have a variety of rulers for accurately cutting out triangles in different sizes.
- Creative Grids also have seam guides in different sizes that make marking the back of your squares easier for sewing half square triangles. Bonus: these take up less room than rulers.
If you are planning a larger project with half square triangles and don’t want to do the math, QuiltMath by Always Expect Moore does it all for you. You’ll always know exactly how much fabric you need. These are the ultimate half square triangle cheat sheets! Full disclosure: Carolina sent me a sample to try out a few years back and these make planning much easier. Watch the video below to see how QuiltMath works.
If you want to increase your accuracy by using paper piecing for your triangles, Triangle Paper can help a lot! This cheat sheet will let you know which size of Triangle Paper you’ll need for your finished quilt block size.
Finally, if you’re not sure how you want to layout your half square triangle blocks, C&T Publishing is about to release a Half-Square Triangle Quilt Block Design Deck with cards you can position endlessly to find the perfect layout. You can buy the Design Deck from independent booksellers or at C&T Publishing or Fat Quarter Shop.
15+ Free Patterns for Half Square Triangle Blocks and Quilts
Now that you know how to make half square triangle blocks in the abstract, and you have all the tools you need to make them perfect, you’re probably looking for some project inspiration. Here are 15+ free patterns for half square triangle blocks — and projects including pillows and quilts — using HSTs.
- Easy Half Square Triangle Pillow by Underground Crafter: This pattern makes half square triangles easy with pre-cut fabric and the Clover No-Hassle Triangle Gauge.
- Churn Dash Block by Cluck Cluck Sew: This tutorial shows you how to make the 9-1/2″ (9” finished) version of this classic block. Allison has several other free patterns including HSTs such as the Easy Pinwheels Block in three sizes and the Sweet n’ Sassy Baby Quilt pattern.
- Twinkle Star Block by Blossom Heart Quilts: This pattern for a 12-1/2″ (12” finished) block is one of many scrap busting block tutorials on Alyce’s blog and also includes a link to AccuQuilt cutting instructions.
- Sawtooth Twist Block by Mary Go Round Quilts: This pattern for a 12-1/2″ (12” finished) block is a variation on the classic Sawtooth Star Block pattern. It includes a downloadable pattern.
- Jewel Box Block by Lee A. Heinrich: This pattern for an 8-1/2″ (8” finished) block also includes instructions for making a baby quilt.
- Shoo Fly Block by Adventures of a DIY Mom: This pattern includes cutting instructions for four sizes of this classic quilt block.
- Striped Sawtooth Block by Lake Girl Quilts: This pattern for an 8-1/2″ (8” finished) block is a variation on the classic Sawtooth Star Block pattern and is one of more than a dozen blocks you’ll learn how to make as part of the free Scrappy Stars Quilt Along.
- 6 Easy Quilt Blocks with Half Square Triangles by Sew What Alicia: Alicia shares six simple layouts for making quilting blocks using HSTs as well as graphics to display how each block would look in a quilt.
- Friendship Star Block by Sew Can She: This pattern for the classic Friendship Star Block makes a 12-1/2″ (12” finished) block and has an option for a downloadable PDF.
- Hidden Safari Party Quilt by Flamingo Toes: This quilt uses a combination of squares and strategically placed half square triangle blocks for an interesting look!
- Sherbet Baby Quilt via Baby Lock: This simple, half square triangle baby quilt pattern includes a quick video tutorial and downloadable pattern instructions.
- Summer Vibes Quilt by Scattered Thoughts of a Crafty Mom: This fun blanket pattern combining squares and half square triangle blocks is in three sizes as a downloadable pattern.
- Herringbone Baby Quilt by Polka Dot Chair: This simple quilt pattern uses HST blocks with an interesting layout for a herringbone look. It includes a tutorial for making 8 half square triangles at a time.
- Mending Basket by Pat Sloan: This tutorial includes downloadable instructions for a 12-1/2″ (12” finished) block and wall quilt.
- 16 Half Square Triangles Sampler Quilt by Teresa Down Under: This tutorial includes instructions for 16 10-1/2″ (10” finished) quilt blocks using HSTs, including video tutorials and instructions for piecing and finishing the quilt.
I hope you’ve enjoyed this collection of half square triangle blocks and quilt patterns, and that you’ve learned something new about how to sew them!