Today I want to welcome Christina Lane to Whipup – an all around crafty gal, she says that she loves everything from quilting, screen printing, embroidery and more! She has recently had patterns published in Quilts and More magazine and Lunch Bags!, a Stash publication. When she’s not creating for herself, you’ll find her longarm quilting for others. Christina loves to share her crafting journey at her blog The Sometimes Crafter.
Hello Whip-Up readers! It’s so nice to be back in this space guest posting at Whipup. Today I wanted to share a really great way of making half square triangles (HST) that I recently found online and give you some measurements to help you with making them just the size you need for your own projects. Ahead of me I have a quilt full of half square triangles, and I was not looking forward to the prospect of making all of them in the way i’m use to. Then I remembered having seen this video by The Missouri Star Quilt Company.
Her ingenious method of assembling a HST (half square triangles) for a pinwheel block is perfect for most HST projects I can think of. You simply take your two squares of fabric (usually a print and a solid), place them right sides together and sew around all four edges with a 1/4″ seam allowance. Then you cut the square on both diagonals and you end up with four pieces.
When you open out and iron them you get perfect half square triangles! It’s amazing every time. I recently made a bunch of these in different sizes just to get a feel for the math. I have some of the sizes figured out to get you started, but the basic math is a HST that is roughly 64% of the size of your original square.
So your math would be this:
Beginning Square Size x 0.64 = HST size.
If you knew the size you needed your HST to be, but wanted to find out how big to cut your beginning squares, you would use this equation instead:
HST / 0.64 = Beginning Square Size.
Of course it’s always a good idea to make a test square before beginning a project, as all of our sewing and cutting varies. Not every size is exactly 64%, but it’s a good place to start without getting too involved in the math. Below is a table that gives you the starting square size and the final HST size for sizes that I’ve actually tested. You may find as you make these that you can get 1/8″ to 1/4″ more from each size, but I like to play it safe. So many times when I’ve made HST in the past I find that I don’t have enough to trim away and get the size stated in the pattern, so i’d rather play it safe. Good luck and have fun creating!
{ 36 comments… read them below or add one }
wow thanks for the tip and for doing the math. I hate calculating so this helps!
best wishes
You wouldn’t believe this but I was just thinking last night that I need to search for this information! I just bought fabric for a table topper and I wanted to design the top but I couldn’t remember the formulas. Thanks for a very timely post!
Nice Math!
I’ve done this before, it’s fast and easy! The cut edges will be on the bias though, so be careful not to stretch them out!
I’ve done a couple quilts based on that video. So easy! Thanks much for the math. Math and I don’t get along, so I’m super excited to have it done for me!
Awesome. I want to quilt, but cutting is not my friend. Fewer cuts means I’m more likely to start (yeah, still haven’t done that) and finish a project!
This couldn’t have come at a better time,thanks! Got all my fabrics stacked up for a HST quilt and needed the math!
It looks very easy! But isn’t your grain in the wrong direction this way???
Be careful with your bias edges – reinforcing with starch will help stabilise while sewing the patches together, otherwise make pins your friends and be careful not to pull the fabric while sewing the patches together.
I don’t understand why we are dividing by .64. Can’t we just add 7/8″ to the finished size? That is how I do it!
If I want my HST piece to be 4″ finished (4.5″ unfinished) then I cut my squares 4 7/8″, draw a diagonal line, and sew 1/4″ from it on either side. When I cut in half and press, my pieces are 4.5″, just as planned.
Wow! That’s the best method I’ve seen yet. Thanks for sharing.
This. Is genius. I am about to start a pinwheel quilt and this will save some serious time!
My jaw just hit my desk. I would never have thought of this. It’s so genius but so simple! Thanks for doing the math…
Thank you soooo much for this post. I have wanted to try this, but just couldn’t get my head around the math!!!
I wonder what the math is for turning these into Pinwheels? I’ve never thought to break it down like this. Thanks!
I tried this method just this week, and it is now my FAVORITE way to do HST. Thank you for doing the math! The blog where I first saw this had math, too. But it was WRONG! Ooops!
I use this method all the time & love it, but I’m not sure it’s a good one for those new to sewing. It’s far too easy to stretch those bias edges.
Great little chart to have handy!
Brilliant!
Yipes! There is a better quick way to do half square triangles where you don’t end up with all that bias all around the outside. If you do it this way, be really really careful with the iron so you don’t stretch the shape. This is a good way to use charm squares like in the video, but if you are cutting your own fabric, I predict less frustration if you do quick-pieced half-square triangles the traditional way.
Thanks so much for the calculation! I also saw that video a month ago and was amazed. Just last night I was wondering how to figure out that math, as i am about to make a block with 5 small pinwheels and thought it would be a perfect time to try the new technique. Thanks!
Yea Christina! I love the inner math geekiness! Thanks for figuring this out…I took a pic of the chart so it will always be available on my phone as a reference! I am sewing my last Neptune charm pack using this technique……thank you for the numbers!
These are actually quarter-square triangles, not half-square triangles. And they have all the outside edges on the bias, so are really tricky for beginners to handle. I wouldn’t recommend this method to a beginner patchworker, as it is a recipe for a really messed-up, discouraging result!
Thanks for working out the math and the chart – I copied and saved it to have as a reference.
I’m not sure it would be a good use of fabric, but here’s a way to use Christina’s math AND avoid ending up with the bias edges on the small squares: cut the big squares on the bias. Proceed as directed, being careful not to stretch the edges as you sew those outside seams.
Wow! What a fabulous idea!
Thanks for sharing.
Thanks so much! This is just perfect…I have to save and print it out so I have it when I start my HST quilt!
I made a wallhanging using this tutorial and it turned GREAT.
http://sewkool.blogspot.com/2011/03/baby-toy-and-wallhanging.html
This works well and if HST are small the bias does not seem to be a problem. There is another way that gives straight grain edges and yields 8 HST. I searched for instructions and the math but could not find a site.
One needs 2 larger beginning squares. Just as in making a single HST mark a diagonal line from one corner to corner and also from the opposite corner to corner. Now stitch 1/4 inch on both sides of each diagonal line.
Then cut vertically and horizontally in the MIDDLE of the square giving four squares that are sewed on the diagonal. Cut between the diagonal stitched lines and there are 8 HST. The only math I could find was for 3 1/2 inch HST start with the beginning two blocks at 8 3/4 inches. It may be helpful to do a bit larger and trim the finished HST.
Thanks everyone for all the super great advice – so great to have so many talented and knowledgeable people able to add to the knowledge base
xx
Oh! I want to remember this! How in the heck am I going to bookmark this comment?
This is awesome! Thanks so much. Can’t wait to try this out. So appreciate your hard work!
Here is one that worked for me… Start with 9 7/8 squares, sew each edge with ¼ seam allowance. You’ll get 4 – 6” finished half square triangle.
My sweet husband worked out the formula for me… Square root of {2*[(Finished square with seam allowance + 0.5) squared]} = the size of square you start with.
Then I put it into excel to get the following measurements….
Basically the numbers in order show the size finished block (1), the block with seam allowance (1 1/2), the starting block size as a decimal (2.82843), and the approx yardage square calculation (2 7/8).
I generally rounded up… and I still have to test them… but here they are… :)
Finished HST / HST w/1/2” seam allowance / Starting Square actual / Starting Square approx. yardage calc
1 / 1.5 / 2.82843 / 2 7/8
2 / 2.5 / 4.24264 / 4 ¼
3 / 3.5 / 5.65685 / 5 2/3
4 / 4.5 / 7.07107 / 7 1/8
5 / 5.5 / 8.48528 / 8 ½
6 / 6.5 / 9.89949 / 9 7/8
7 / 7.5 / 11.31371 / 11 5/16
8 / 8.5 / 12.72792 / 12 ¾
9 / 9.5 / 14.14214 / 14 1/8
10 / 10.5 / 15.55635 / 15 9/16
11 / 11.5 / 16.97056 / 17
12 / 12.5 / 18.38478 / 18 1/2
I could cry…no really. Thank you so much for posting this. I am going to be making a quilt from all the scraps I have left over from sewing for my daughter when she was little. I was dreading doing the hst because they always turn out wonky for me. Thank you so (sew) much!
P.S. I found you on Pinterest
I’ve been making HSTs this way since being introduced to the video on Missouri Quilt Company. As a newish quilter, I don’t know alot about bias, but I haven’t had any frustration in making blocks this way. Someone contacted me via flicker wanting to know how to make the block. I posted the link to the video, then remembered I’d seen this on Pinterest, and shared the link. I’m working on a diamond quilt block using this method now:
http://mandamadequilts.blogspot.com/2011/09/diamond-rainbow.html
THANK YOU for posting this. So glad you figured the math out for me.
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