Half Square Triangles in Half the Time!

A qick tutorial on how to trim half square triangles faster

I know I’ve completely lost it—this is the third pinwheel/half square triangle post in the past few months, but I have my reasons:

-You’re going to get an awesome new pattern later this month that includes *some* pinwheels, so you’re welcome in advance!

-I’ve made about 560 Half Square Triangles (140 pinwheels) in the past month, so I probably have lost it a little…

-I’ve got one more post on giant Half Square Triangles coming up, so just settle in.

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how to make perfect pinwheel blocks fast

So many pinwheels, are you dizzy yet!?

If you haven’t been around the blog in a while, no problem, let me get you caught up!

  1. First, I posted about making half square triangles fast using the Magic 8 Method. This was a pretty fun post and I’m really enjoying hearing about how it’s changed your pinwheel making experience!
  2. Then, I followed up about how you can get the perfect pinwheel, which has a lot to do with a special pressing technique that allows your centers to sit flat.
  3. Now we are back on Half Square Triangles and how to make them even speedier!
  4. In a few weeks I’ll be showing you how to cut HUGE pieces on the bias without distorting or stretching. (Update: Here’s my post on How to Cut Large Triangles (on the Bias) and Keep Things Straight.)

Making Half Square Triangles FAST

The actual making of your Half Square Triangles is already as fast as it can get when you use the Magic 8 Method that I showed you a few weeks back. But what about all that trimming?! Don’t worry, you’re not alone, I hate this part SO MUCH!

fast half square triangles

So what’s a girl to do? Find a way to cut that time spent trimming in half!

Trimming Half Square Triangles FAST

Save the Trimming for Last

Yep, you read that right. Keep on sewing and *then* do your trimming. Here’s why:

Typically, you’re going to end up sewing at least two Half Square Triangles together (if that’s not the case for you, skip to the “Tools” section of this post). What I like to do is sew my two HST’s together and then trim. Why trim one block at a time when I can trim two!? Here’s how I do it without skimping on precision:

I don't trim my half square triangles!

Sew the Half Square Triangles Together

First, I simply sew the HST’s together. Since I haven’t trimmed things up yet, I make sure that my seams line up nicely by fitting them together and feeling for them to “lock” into each other. Getting this part right is vital to getting a precise point later on, so don’t be lazy with this step!

how to line up half square triangles

I sew down the edge with my 1/4″ foot. If I’m doing a lot of these, I’ll chain piece as I go to save time too!

how to piece half square triangles fast

How to Trim 2 Half Square Triangles at Once

Now that I’ve sewn two pieces together it’s time to trim (Put that iron down! It’s not time for pressing yet!). Here’s where nifty tools are always helpful (but not required).

First, line up the 45 degree line of your ruler with the stitches running through the middle of your block. Next, slide the edge of your ruler to be flush with the sewn edge. Before cutting, make sure that you’re still lined up on the 45 degree mark. The only part that you’ll be trimming from this side is your dog ear! Trimming off any fabric from this edge will mess with the final size of your block.

the quickest way to trim half square trianges

Then, trim the remaining three sides of your block to the block size listed in your pattern.

how to trim lots of half square triangles

That’s all there is to it—I’ve gotten great results with this technique and saved a ton of time. I mean, look at those points!

making perfect points with half square triangles

Helpful Tools for Trimming Half Square Triangles

I’m typically pretty anti-tool, and especially anti-ruler. I’ve got so many supplies and rulers floating around the studio…I don’t need one more. But either of these tools will make your life a lot easier when trimming HST’s and other blocks.

Bloc Loc Rulers

These little guys are the bomb. I don’t personally own one, but I’ve used them and they are amazing! They have a small ridge on them that “locks” into your 45 degree seam, and since the ruer is sized to the finished size of your block, trimming is a breeze!

You can easily find these on Amazon as single pieces or in sets!

Tucker Trimmer

I personally own the Tucker Trimmer and love it because I can use it on lots of different sized blocks, rather than having one for each size. It’s really simple to use and takes up very little space!

So there you have it! Now you now how to make half square triangles FAST, trim half square triangles FAST, and press PERFECT pinwheels. I’m getting dizzy with all these pinwheel posts!

Until next time, happy sewing!

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A qick tutorial on how to trim half square triangles faster


  1. Great tip Rachel! I, too, lock two HSTs together at a time to trim, but I do it before sewing and trim them to size. I first saw this on Alex Anderson’s ‘Simply Quilts’ show many years ago, and it cuts the HST trimming time in half, with no need for the bloc loc ruler. 🙂 I’ll have to try your method now too! btw Deb Tucker does some amazing stuff – I made her migrating geese as one of my RSC projects last year. 🙂

    • Thanks so much Sandra,
      I’m always a little hesitant to post things that I try and think are brilliant, because (usually) I come to find it’s already been done! I’m glad to hear I at least added something new for you though 🙂
      I love Deb Tucker! I wish I had more time to do a deep dive on her work, tools, and such!
      Let me know how it goes when you give it a try 🙂
      Until then, happy sewing!

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