How to make Half-Square Triangles (HSTs) – eight at a time

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. For beginner quilters, we recommend you start with making them two at a time. If you’re using a charm square pack, you may like to make them four at a time. But sometimes quilters need LOTS of HSTs, so why not follow this method to make them eight at a time! 

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. On the back of one of the squares (usually the lighter fabric), mark a line on both diagonals with a pencil or hera marker to dissect the square into four triangles.

Step Two

Sew a seam one quarter of an inch (¼”) away from each drawn line on both sides of each line.

Step Three

Using a rotary cutter or scissors, cut the square in half vertically and horizontally. Each quarter will look like a regular HST unit. Cut each quarter along the diagonal line to produce two HST units from each pair of squares, or eight HSTs in total.

Step Four

Press your HST units open, pressing 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 Five

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

Essentially, all you’re doing with this method is making four of the two at a time HSTs, which mean that we need to double the measurements we would use if we were only making two HSTs of the same size. We have rounded up to the nearest inch 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, four 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 and lots of little HSTs in repeating fabrics. 

The Half Square Sampler Quilt, shown below, is a great project for beginner quilters to really get the hang of making HSTs, a block that you will find used widely in the quilt world.

Half Square Sampler Quilt

Published in Make Modern Issues 37 to 42

By Rebecca Cottongim

Zella Quilt

Published in Make Modern Issue 40

This is another project that uses lots of HSTs in repeating fabrics. The eight at a time HST method is perfect!

By Sarah Campbell