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If you’ve been quilting for more than 5 minutes, you’ve probably made a HST (Half Square Triangle unit) a time or two (or hundred or thousand.) There are actually several ways to make them, but today I thought I’d show you the most common way to do it. Just in case you’re not sure what I’m referring to, a HST looks like this, and we tend to use them A LOT in quilting:
Each square is cut in half into 2 triangles, and then sewn back together to form a square.
I really like to make my units a little big and then trim them down to the perfect size- I find that no matter how careful I am with cutting, pinning, and sewing, my units can end up a little wonky. (Some people use starch to make their units behave… which is a fine solution… I just don’t like to have to clean my iron.)
I’ve made up a PDF “Cheat Sheet” for you- it’s basically a guide so you can tell at a glance what size to cut your squares for making HSTs. PLEASE NOTE- I NOTICED AN ERROR IN MY ORIGINAL CHART- PLEASE MAKE SURE YOU HAVE THE ONE THAT SAYS “REVISED.” THANKS!
Let’s go over how to use the chart!
You can choose whether you want to make the HST the exact size you want it to be, or if you want to make it a little big so you can trim it down.
Look on the left side of the chart- the 2 yellow columns will show you the size of the HST when it’s done (I’ve given you measurements with and without seam allowance, because I know sometimes my brain doesn’t want to do that extra little bit of math, and I figure that some of you are the same way, LOL.) So let’s say you need your HST’s to be 5″ in your quilt- that means you need them to be 5 1/2″ with the seam allowance. Find that measurement in the chart:
Then just look to the right, and choose the measurement in the first white column if you are making them to the exact size. Choose the measurement in the second white column if you are making them larger for trimming. This is the measurement that you will cut the squares.
If you need an unusually sized HST (5 3/8″?? 3 7/8″???), I’ve also included the FORMULA at the bottom of the chart for calculating what size squares to cut. (Sorry- you WILL have to do the math for this) I’ve included the formulas both for making the HSTs to the exact size needed and for making them a little big for trimming:
Now, let’s make some HSTs using the chart! Remember that however many squares you cut, that is now many HSTs you will end up with. So, if you cut 2 squares and sew them up according to this method, you will end up with 2 identical HSTs. If you cut 50 squares and assemble them according to this method, you will end up with 50 HSTs.
As I mentioned, I like to make mine a little big and trim them, so that’s how I’m going to make mine. Using the example above, I want my HSTs to be 5 1/2″ (so that their finished size in my quilt is 5″.) So, I’m going to cut 2 squares which are 6 1/8″.
On the WRONG side of the fabric, I will draw my line down the center diagonally, which will be my cutting line. Then I draw a line 1/4″ from the center line- these will be my sewing lines. (You can skip drawing those sewing lines if you want, and rely on your 1/4″ mark/guide on your machine. But I like having the lines there to insure accuracy.) I found this nifty little ruler which makes it really easy to draw your lines.
Pin 2 squares RIGHT SIDES TOGETHER. I will sew on the side lines, and then cut the center line:
I open them up and press- depending on the pattern, sometimes I press the seam open, and sometimes I press it to the darker fabric.
Now, if you chosen to make them to the exact size, you would just trim off those “dog ears,” and you’re done.
But since I’ve made mine a little big, the measurements in the chart have resulted in HSTs which are about 5 3/4″, so I’ll trim them to my desired 5 1/2″. A note about trimming the HSTs- be sure to use the 45 degree line on your cutting mat, or on your ruler. This will assure that you have PERFECT HSTs:
Now I have 2 pretty HSTs.
That’s it! Click here for a downloadable PDF of the cheat sheet, then print it out and put it next to your cutting table for easy reference!