Tutorial: Half Square Triangles with the Cinnabar Quilt

Hi friend!  Are you ready to make your own Cinnabar Quilt that is sure to be a work of art?  Creating this quilt may seem like a daunting task, but fear not!!  Half square triangles are a fundamental building block of this quilt, and the good news is that they're relatively simple to make. 

With just a few basic sewing supplies, some careful measurements, and a bit of patience you’ll be sewing your eye-catching Cinnabar Quilt together in no time. 

In this blog post, we'll take a look at how to make half square triangles using the four-at-a-time method, a simple and effective way make the most versatile Quilty component.  We'll provide you with step-by-step instructions (and be sure to scroll down to the cheat sheet at the end of the post to make half square triangles in whatever size you need). 

Cinnabar Quilt

The Cinnabar Quilt calls for 3-inch finished Half Square Triangles (HSTs), so this blog post will reference that size throughout.  Note:  If you’re using this blog post to help you learn how to make half square triangles but you are making a different size - the steps are the same, just be sure to use the chart at the bottom to calculate the beginning size square you need and then make sure you are trimming to the right size.

You’ve picked out and cut your fabrics, and you are ready to dive in and make all of those HSTs….yay!  Follow the chart in your pattern to pair up your fabrics and let’s start sewing!

Making Half Square Triangles

In short, to make HSTs using the four-at-a-time method, you will take two large squares, sew around the perimeter, then cut from corner to corner in the shape of an ‘x’ to make four Half Square Triangles per fabric pairing.  Let’s break that down.

The Cinnabar Quilt uses 5 3/4” large squares to make 3 1/2” unfinished HSTs.  Take your fabric pairs and pin them right sides together.  Next, sew a 1/4” from the edge of each pair.  Tip:  Chain piecing really speeds this up!  Chain piece one side of all pairs, then the second side of all pairs and so on until you have sewn a 1/4” around the edge of each pair.  

Then, cut the sewn squares from corner to corner to make an “x”.  I prefer to use a rotating cutting mat for this process.  A rotating cutting mat allows you to make the cuts you need without having to reposition the fabric.

You will now have four Half Square Triangles for each sewn pair.  It is time to press those seams and trim.  Again, for the Cinnabar Quilt, we’ll trim each HST to 3 1/2”.

If you’re making the Twin sized Cinnabar Quilt like I am, you’ll need 360 HSTs!  That will give you a lot of practice.  And to make the process a little easier, I recommend purchasing a specialty ruler for cutting HSTs.  There are several available for you to choose from.  I picked out a ruler that is for 3 1/2” and smaller which allows me to trim either before or after pressing.  

Cinnabar Blocks

If you’re making your Cinnabar Quilt right along with me, it’s time to take all of your HSTs and sew them into your gorgeous blocks!  And these Cinnabar blocks are BIG…as in 24 inches big :).  

Lay out your HSTs and background pieces following the instructions in your pattern.  You’ll sew up half blocks first and then sew them together to finish your block.

A love letter to Half Square Triangles

This simple, foundation block is the most versatile block in quilting history!  Beginner and Advanced quilters all seem to share a love for this simple block.  There are 100s of quilt combinations that you can make with this simple component - so don’t let the party stop here.

When designing a quilt pattern, the four-at-a-time method is my go-to for HSTs!  You can save or download the chart below to help you determine how much fabric you need for the size HST you are looking to make.  Or, if you have some pre-cuts laying around.  Use the chart below to see what size HSTs you can make with little or no prep and cutting.

Need additional sizes?  You can determine any size HST with some simple algebra.  You can use the following equation, assuming x = beginning square size (big square) and y = unfinished HST size.  y = 0.7071x - 0.3535.

When creating the Cinnabar Quilt, half-square triangles are essential components. With some practice and patience, the results are undeniably worthwhile for a stunning quilt. Grab your ruler and rotary cutter and let’s get quilting!

Looking for the Cinnabar Quilt pattern?