The Ultimate Half Square Triangles Tutorial
Half Square Triangles are a very versatile quilt block. They are used in numerous quilt blocks and can make striking quilts on their own. There are also multiple ways to make HSTs and this post will show you the most common ways to make them.
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Table of Contents
Paper Pieced Half Square Triangles
I use paper pieced HSTs when I need to make small half square triangles. It allows me to use bigger pieces of fabric and it makes them easier to sew.
I just needed a few half square triangles of each color for this mini quilt that I made so I used Generations Quilts papers. If you need a lot of HSTs I recommend buying the papers per printed from Fat Quarter Shop. They have papers that are designed to use with pre cut fabrics and for specific sizes of HSTs.
HSTs One At a Time
Sometimes you need a variety of triangles and sometimes you need to use up those bonus triangles that are created from snowballing other quilt blocks.
Bonus Triangles
If you are using bonus triangles all you have to do is match the raw edges and sew. There are a few things to keep in mind though. That diagonal edge you are sewing is a bias edge. If you aren’t careful it will stretch and change shape.
Cutting Triangles
When I’m cutting HSTs one at a time I always starch my fabric because of the bias edges I mentioned earlier. Starch helps keep the stretching down but you do still want to be careful when handling that edge.
If I’m cutting triangles I prefer to use an Accuquilt Die. The dies allow me to cut many triangles at once and they let me use up smaller scraps.
If you don’t have an Accuquilt and it isn’t in your budget right now this ruler from Creative Grids is perfect. It has four different ways you can use it so you won’t have a ruler for only one job.
Half Square Triangles Two at a Time
HSTs two at a time is the most common way to make half square triangles. There are some variations to this method though. Some folks use will use strips of fabric but that puts the bias edge on the outside of the block and not in the seam. I do my best to avoid having bias edges on the outside edge of blocks so I don’t use this method.
Instead, I use two squares that you sew on either side of the middle and then you cut down the middle for two units.
In the video above I show you ALL the steps including the math for what size to cut your squares. I don’t like adding 7/8 to my finished size for a couple of reasons. The first is it makes the math complicated if you need something like 4 3/4” for your finished size and if you aren’t the best at sewing 1/4” seam it leaves little wiggle room. I prefer to trim down and waste that fabric than waste a bunch of fabric because I can’t use the finished unit.
Size Chart
If you do want to use the 7/8 but don’t want to do the math I have this handy chart for you.
No Line Half Square Triangles
You can skip drawing lines on the back of your squares by making a jig of sorts. All you need is your quilting ruler, painter’s tape, and a pen. I was watching American Woodshop and he was showing how to make jigs for woodworking. I quickly realized I could use the same theory in sewing.
You are able to do half square triangles as big as your sewing table will allow. This method also works great when you are doing snowball corners.
Eight Half Square Triangles
If you are doing a quilt project that needs a bunch of half square triangles all the same the absolute best way to do them is eight at a time. I originally called this “The Magic 8 Half Square Triangle” method. It’s kind of magical the way this is so easy to do.
Update to the method
If you are here from a bookmark or a pin to the old original post you are going to notice in the video I am doing it a little different than I used to. The reason I’ve changed up the method is to make it easier to sew. Over the years I’ve seen too many quilters sew on all the drawn lines and end up having a date with Jack. No one wants to rip out stitching so I have modified the method to keep that from happening as often. If you still need those mid-lines for cutting draw them on AFTER sewing.
The Method
We start by drawing an X on our square and sewing on either side of the line. Then we cut down the middle both ways and on the lines we sew lines that we drew. That’s all it is! Easy, peasy, lemon squeezy.
Half Square Triangles 8 at a Time Math
We have to do math in quilting and I like to do simple math. There are two math formulas you can use depending on how much you want to be able to trim away. Both of these methods are based on knowing what size of half square triangle you need to end up with.
Formula 1 – Most Fabric to Trim
Add 7/8” to the size of block you need and then multiple that number by 2. For example, if I need 3 1/2” squares I would add 7/8” to 3 1/2” which is 4 3/8“. Then I would multiple 4 3/8” by 2 for 8 6/8” which reduces to 8 3/4” blocks that I need to cut.
Formula 2 – Least Fabric to Trim
For this formula we are only adding 3/4” but will follow the same steps as formula 1. Again I’m going to use the example size of 3 1/2“. 3 1/2” plus 3/4” is 4 1/4” and 4 1/4” times 2 is 8 1/2“.
I get if you don’t want to do the math so if you join our newsletter you’ll get both the chart for 2 at a time and a separate chart for 8 at a time with both formulas shown.
Trimming Half Square Triangles
No matter what method you use you will probably need to trim up your half square triangles. There are a few exceptions of course. Getting your blocks trimmed correctly will keep you from pulling your hair out.
I love using the Quilter’s Select squares for this. They have a coating on the back that keeps them from slipping and they are easy to read.
What Can I Make with Half Square Triangles?
You can make just about anything with HSTs. The mini quilt above is just half square triangles laid out to look like a swirl. You can turn your half square triangles into hourglass quilt blocks.
