Below are two great Make Modern quilt projects that use the four at a time HST method, but there are lots more in our Pattern Gallery.
How to make Half-Square Triangles (HSTs) – four at a time
Tips
Posted on 07th November 2022
Half square triangles (HSTs) are one of the most popular units for quilt blocks due to the versatility of designs that they can create when a bunch of them are arranged. From stars, to diamonds, to chevrons, these little guys can pretty much do whatever you want them to do! Follow this tutorial to learn how to make quick pieced half square triangle units, four at a time.
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Step One
Half square triangle (HST) units are basically two 90 degree triangles sewn together. However, rather than stitching two triangles together, it’s much easier and more accurate to start with squares. With this ‘four at a time’ method, you start with two squares of fabric, and end up with four HSTs. This is the best method for quickly creating multiple HSTs. It is important to note that the HSTs will have bias edges and may stretch if you’re not careful with pressing or sewing, but it’s definitely nothing unmanageable. If you are a beginner, we recommend you start with our tutorial for making HSTs two at a time first.
The first step, after working out what size HSTs you want to make, is to cut two equal-sized squares of fabric and place them one on top of the other, right sides together. Sew right around the outside edge, a quarter of an inch (¼”) in from the edge.
Step Two
Using a rotary cutter and a quilt ruler, cut along each diagonal to produce four HST units.
Step Three
Remember that your HSTs have bias edges and are easy to stretch out of shape. It’s really important that you carefully press your HST units at this step. Don’t IRON back and forth like you would when ironing clothing, just press down with a hot iron and no steam. Press seams either open, or toward the dark fabric (this is usually recommended as it will help you to nest your seams when you sew them together later).
Step Four
Using a quilt ruler, trim your HSTs to the required size, making sure that the diagonal line is exactly in the centre of your half square triangle unit. If you have lots of HSTs, it can be tempting to skip this step. However, it’s important for accurate piecing, and will make your finished quilt look a lot tidier. A rotary cutter and a rotating cutting mat will make this step easier, and you can even buy special HST quilt rulers for increased accuracy and to speed up the process.
Handy HST Math
When making HSTs two at a time, you need to add an inch to your finished HSTs to work out how large to cut your squares to start with. However, the math to work out the size of the squares you need to begin with when making four at a time HSTs is a little more complicated and takes us back to high school algebra. Our Maths & Methods Columnist Alyce Blyth from Blossom Heart Quilts explains the math behind this method in Make Modern Issue 3 or use this table to see what size to cut your fabric squares. We have rounded up to the nearest half-inch (½”) for easier cutting and wiggle room so you can trim them down more accurately.
There are many other ways of making HSTs – the most common, two at a time, eight at a time, and even strip pieced HSTs. Each method has pros and cons but this one is great if you need to make lots of small HSTs. It’s also really handy if you’re wanting to use charm packs, as a 5″ square will make four 2 ½” finished HSTs.
Once you’re done making your quilt top, get some inspiration for how to quilt them with our favourite motifs for quilting HSTs by our Quilt Like a Rockstar Columnist HollyAnne Knight in Make Modern Issue 39.
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