How to make 4-at-a-Time Half-Square Triangles + Math Cheat Sheet

Today, I’m popping in to share some more practical tips and tutorials that I would have loved to know about when I first started quilting! Knowing how to make 4-at-a-time half-square triangles would have been a game-changer to learn early on.

As you know, half-square triangles (HST) is where my quilting journey started (you can see my first quilt here). I didn’t have a clue about chain piecing or nesting seams or even the need to trim your dog ears. Everything was new to me.

The only thing I knew was that I LOVED piecing, and seeing simple squares get turned into these fun HSTs that could then be used to create even more fun blocks was just the bee’s knees to me!

One of the first commissioned quilts I made was my Blue Odyssey quilt, which was ALL about HST. It would have been so handy to know different methods for pulling so many HSTs together. But I didn’t at the time and made them with the trusty 2-at-a-time method I shared with you a few weeks ago. Knowing how to make several HST in one go is super handy, so today, I thought I would share with you the 4-at-a-time method with you 😊

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MATERIALS & TOOLS

You don’t need any fancy tools to get started making half-square triangles – here are the essentials:

• 2 squares of different coloured fabric of equal size (more on sizing in a minute).
• A Sewing machine – I sew on a Juki TL-2010Q and use a 2.0 stitch length when piecing.
• Pins (optional) – but if you’re just starting out, pinning reduces shifting, which leads to more accurate outcomes.
• Thread for piecing – I stitch with 50wt Aurifil Thread in either white or cream.
• Quilting ruler
• Half square triangle ruler – optional
• Rotary cutter
• Cutting mat
• Rotating cutting mat – optional but makes trimming super speedy! (You can read why I love it here!)
• Iron
• Wool pressing mat – use code SHANNONFRASER15 to save 15% on your small, medium, or large wool pressing mat at thefeltstore.ca or thefeltstore.com.
• Tailor’s clapper – not required, but it can help get some nice flat seams.

I typically stitch with a scant ¼” seam allowance (see my post here for tips on measuring that!)

Now that you’ve corralled your materials and tools, let’s get stitching!

FABRIC MATH & HALF SQUARE TRIANGLE SIZES FOR THE 4-AT-A-TIME HST METHOD

I’ve seen lots of different math formulas out there for the 4-at-a-time method. It seems no matter what technique you use, it all results in lots of weird decimal sizes for your starting square size.

To help keep this as simple and straightforward as possible for you, I’ve gone ahead and done the math for you and then rounded it up so that you’re working with more typical cutting sizes like ½” and ¼”.

In case you need to figure out a starting square for a finished HST that is larger than 10”, then here’s how that would play out.

The formula for 4-at-a-time half square triangles is to divide your unfinished HST by 0.64.

For example, say I want to make (4) 3” unfinished HST (they would finish at 2.5”), then the formula is: 3/0.64 = 4.6875

I like to round up, so that would make my starting square size 4.75”.

Note this calculation method doesn’t leave you with a ton of trimming wiggle room. So, if you want more room to trim your HST down, then I recommend increasing your starting square by a ¼”.

This calculation method is a little more complex, but you’ve got this!

STARTING SQUARE SIZING CHART

To help you in your HST journey, here’s a handy sizing chart in case you want to make ALL the different HST sizes 😉

HOW TO MAKE 4-AT-A-TIME HALF SQUARE TRIANGLES

STEP 1

Once you’ve identified the size of HSTs you want to make, the first step is to cut your squares. For each 4 HST, you will need 2 starting squares of the same size.

Here, I’ve opted for floral and a low-volume print

Place your two squares right sides together (RST) (i.e. good sides facing one another). Pop a pin in the center to help keep your squares from shifting on you.

STEP 2

Stitch a ¼” around the entire perimeter of the square. This is where knowing you’ve got an accurate ¼” SA is handy.

STEP 3, 4 & 5

Make two diagonal cuts, creating 4 individual HSTs.

STEP 6

First, set your seam by placing the iron on your stitches.

Then, finger-press the fabric back, making sure not to pull on the material, before pressing the seam flat with the iron.

To help your seams nest, you want to alternate pressing your seams to the dark and light side.

If you want your HSTs extra, extra flat, then consider using a tailor’s clapper.

Trim your HST to your required size.

And you’re done!

How easy was that?

SEE HOW TO MAKE 4-AT-A-TIME HALF-SQUARE TRIANGLES IN ACTION

I know how helpful it can be to see a quilting technique in action, so I filmed this quick video tutorial for you!

The video also includes two ways to trim your HST using a regular ruler and this specialty half-square triangle ruler.

Your turn!

Have fun stitching these up and creating adorable fabric combos. Just beware, they’re addictive – ha! Good thing you now know how to make 4-at-a-time half-square triangles!

What’s your favourite way to piece HST?

Happy quilting!

xo

Shannon

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