PM/GC Quilts Skill Builder Series: Part 1 – Half Square Triangles & Pinwheels

Oof, that’s a long title, isn’t it? But it’s nothing compared to this post. Just for the record, I’m starting to write it at 7:40 – let’s see how long it takes…

Pinwheels are made of half square triangles, one of the most basic components of traditional type quilt blocks. There are many ways to make HSTs, and between Jeanne and I we’ll show you four methods.

Here is Jeanne’s post with the other two construction methods.

You’ll make four pinwheels and then sew them together into a single block that looks like this:


The traditional method for making half square triangles (which Jeanne is showing you over on Grey Cat Quilts), involves a precisely measured square cut diagonally, matched with another triangle, then sewn together along the bias edge. The challenges include accurate measuring to the 1/8th of an inch, handling bias edges which are much stretchier than straight of grain edges, and accurate quarter inch seams. The accurate measurement and seam allowance can be avoided by deliberately cutting the squares larger than needed, then trimming the finished HST to size, but you’re still dealing with the bias edge.

Method 1: Papers

When I’m making HSTs, I consider the project before I decide my method. If my project requires a lot of identical HSTs, I go right for the Triangle Paper. There are different products that do essentially the same thing, including Triangles on a Roll and Thangles. I prefer Triangle Paper, but that’s just me. With Triangle Paper I can make a lot of HST units very quickly with relatively little accuracy required. It’s literally sewing and cutting on the lines. These products come pre-printed in many different sizes. You can also purchase a computer program called Triangulations that will allow you to print papers in any size you need.

While you can cut the papers apart to make just a few HSTs, I’d rather not waste them and use my second favorite method. If I just need 2 HSTs, or if I’m making a project that uses different combinations of fabric in the HST units, my method is similar to the traditional way, but instead of cutting triangles then sewing, I sew the triangles, then cut. This way I secure the bias edge with a seam before it is exposed by cutting.

I’m going to tell you right now, like many quilters I struggle with a perfectly accurate 1/4″ seam. We’ll get into that in a later (but not too much later) Skill Builder post. Rather than agonize over my seams, I prefer to cut the components larger then trim to size after I’ve sewn them. Yes, it means a little extra time trimming. I believe I spend less time trimming than I would ripping and resewing, so I think the trade off is worth it.

So, on to my HST methods!


Since I can’t expect everyone to run right out and purchase Triangle Papers just to make four HSTs, I’ve created a smaller version and made a PDF for you to download. One sheet will make eight HSTs that finish at 3″.

Terminology clarification: When a block or component “finishes” at a size, that is the size it will measure after it is sewn into a finished project. The component or block will measure 1/2″ larger than the finished size. So a 3″ finished HST will measure 3 1/2″ until you sew it into a block.

Although the sheet makes eight HSTs, you only need four for one pinwheel. Cut the sheet in half and save the other half for another project. There is a 1″ guide on the PDF – make sure that the box measures exactly 1″ on your paper before you use it. If it doesn’t, check your printer settings for page scaling or page size adjustments.

Choose two fabrics for your pinwheels. Fabric selection will be the subject of the next Skill Builder, but for this one I recommend choosing fabrics that have a pretty good contrast. You want to be able to see those lovely points and pinwheels you’re going to make! Also, in order to make nice neat points and press everything easily, try choosing one fabric (or one type of fabric, i.e. print, solid, small scale, etc.) to use in all four blocks as your background, then four other fabrics for the pinwheels. In the picture above my “background” fabric is the print.

Cut a piece of each big enough to extend a little bit past the paper. Place the two fabrics right sides together then lay the paper over them. Keep the square lines going the same direction as the grain of the fabric. Pin in a couple of places that won’t interfere with your sewing. Make sure the fabric stays flat and doesn’t pucker or twist when you pin it. You can lessen the number of times you stick yourself with the pins by pointing them all to the left or to the right.


Set your stitch length a little shorter than usual (I used 2.0 instead of 2.5) to make tearing the paper easier. Sew just inside (toward the seam allowance) the thicker blue lines. Look closely at the photo to see where I place the foot in order to get the stitching just at the inner edge of the line.


Your machine’s foot may look different from mine – experiment with placement until you see how your foot lines up with the needle. As you sew, watch the line where it meets the foot, NOT where it goes under the needle. By that point it’s too late to make any corrections. Ooh, that’s a good one, so I’ll emphasize it…

Sneaky Little Quilting Tip: As you sew, watch the line where it meets the foot, NOT where it goes under the needle. By that point it’s too late to make any corrections.

If you’re wondering why I sewed just inside the blue line instead of directly on it, it’s one of those perfect quarter inch seam allowance things. Folding the fabric back takes up a little space, as does the thickness of the thread. Sew a little inside the line and everything comes out better. (That one’s worth emphasizing, but I’ll do it in the quarter inch post!)

After you’ve sewn all of the blue lines, cut on all of the black lines. That includes the outer edges, the center + lines and the diagonals between your seams. By the way – before you cut your diagonals, notice the size of the square:


It’s exactly 3 7/8″, the size you’re supposed to cut your squares before cutting them diagonally when making HSTs the traditional way. But you didn’t have to measure that, because the paper did it for you.

When you’ve cut all of your pieces apart it should look like this:


Fold the paper back and crease it a bit along the sewing line.


Rip the paper off (it’s easier to hold the smaller side and pull the larger side). Try not to pull out stitches. Because you’ve reinforced the bias with the seam, your fabric won’t stretch unless you break or pull out the stitches. This is a good project for sitting in front of the tv or if you have kids you can delegate it to.


Oh, I’ll bet a couple of you just swore at me! “Press” is a loaded word. Press how? Open? To the side? Which side? Why?!?!! I’ll start with open vs. side: Both are right. Yep, I said it. Your quilt will not disintegrate into tiny shreds if you press your seams open. Your quilt will still look awesome after it’s quilted if you press your seams to one side. I do both, depending on the project. If I’m working with very small pieces, I nearly always press open because it’s easier to keep the blocks flat. With larger projects I tend to press to one side because I like nesting my seams together, and I’d rather work without pins when possible. Whoops – there’s another one! Pinning…

Some quilters like to pin the heck out of their pieces. Give it a try, that may be what works best for you. Also try different size pins – thinner, longer, etc. Don’t be afraid to try sewing without pins, too. With the seams pressed to opposite sides the two pieces nest neatly together and keep the fabrics from sliding. I find that pinning tends to make my fabric buckle and I’m less accurate. Check my finished block – it was all sewn without a single pin, and the points look pretty good to me.

The trick in pressing to one side is to know which side to press to. I confess I still don’t always have that figured out in advance, so I’ll find myself re-pressing as I make a block. Pressing is another good subject that we’ll address in a future Skill Builder. For pinwheels, choose one fabric and always press to that one. In this case, you should press to your background fabric. I used the print fabric in all four pinwheels, so when I joined those pinwheels all of the seams were going the correct direction.

Once your HSTs are pressed, trim the dog ears and trim to size, if necessary. They should measure 3 1/2″.


Your first four HSTs are finished! You’ll sew them into a pinwheel, but before I show you how to do that, let’s try the second method.

Method 2: Squares with Diagonal Lines

In this method, you’ll cut squares that are a little larger than necessary. If you’re making a 3″ finished HST, the traditional method has you cutting the squares at 3 7/8″, then cutting diagonally. (The traditional rule is to add 7/8″ to the finished size.) I like to add 1 1/4″ to the finished size when I cut my squares. That gives me enough extra that my cutting and quarter inch seam don’t have to be perfect, and the HSTs will be large enough that I can see what I need to trim. If you’d rather, you can try cutting 1″ larger, but you’ll need to be more precise.

So… cut two 4 1/4″ squares of each fabric.


On the back of one of the fabrics, draw a diagonal line, then draw a line 1/4″ to either side of that line. If you prefer you can omit the center line and just line up the ruler’s 1/4″ line at the corner points.


I used a SewLine Fabric Pencil with white ceramic lead (and I love this product!), but on lighter fabric a regular mechanical pencil works just fine. Hold the ruler firmly and try not to stretch the fabric when you draw the line. Short, light strokes are best, even if you have to go over it a couple of times to make the line dark enough.


Sew on the two outer lines. Unlike the Triangle Papers, you can sew directly on the lines, since you have a little extra fabric.


When you’re finished, cut on the diagonal line in the middle. It doesn’t matter if you cut exactly on the line – the sewing lines are the ones that need to be accurate. Sometimes I just use scissors for this.


Press your HSTs (see above!). They’re larger than the 3 1/2″ you need, so you’ll have to trim them to size. (I’m left handed so some of my photos will look really wrong to you. I rotated the photos here to show you a right handed perspective.)


When you trim the HSTs, use the diagonal line on your ruler as a guide. Line it up with you seam then see how much extra you have to trim. I prefer to cut about half of the extra off of each side (rather than most off one side and little off the other). I think it helps me be more accurate.


Sneaky Little Quilting Tip: Look closely at the fabric under the ruler at the left side. See the cut edge in relation to the lines on the ruler? Measure from the outside of the line on the ruler, not the inside. It’s just a couple of threads, but it makes a difference.

Now you have two sets of half square triangles. It’s time to make pinwheels! From this point forward, the pinwheel construction method is the same.

Lay your four HSTs out next to your sewing machine. Make sure the HSTs are turned in the correct direction to form a pinwheel. This is important: the background fabric, the one that is the same in all of the HSTs, should be at the top of the top left HST. It sounds confusing, but look at the photo and use the print as your guide.


Turn the top right HST over on top of the top left HST. Keeping the pieces oriented in the right direction, slide them together until the right edge lines up and the seams nest together tightly. When you squeeze the seam between your finger and thumb it will feel flat. If they aren’t nested tightly you’ll feel a gap and if they’re overlapping you’ll feel a bump.


Pin if you like, then sew. Watch your quarter inch seam here. (I know, I know – that post is coming soon!) When the first two HSTs are nearly sewn together, leave them under the foot and pick turn the bottom right HST over the bottom left HST. Nest, squeeze, and pin if you like, then lift the foot a tiny bit and place the squares just under the front edge of the foot.


Sneaky Little Quilting Tip: If you lift the foot a tiny bit, you’re less likely to push the top layer of fabric out of alignment. This also helps prevent the machine from eating a point when you’re sewing triangles. It takes a second longer than just feeding the next edge it, but it’s worth it.

Sew the second set of HST units. I like to leave the little chain of thread connecting the two pieces. That ensure that I don’t accidentally turn one of the sets upside down.


Look closely at that photo above. See how the seams intersect, one straight, one diagonal? That is a magic arrow that shows you exactly where your next seam should go. If you sew across that arrow, you’ll cut off a point. If you sew just a hair past the tip of it, your points will be beautiful. The thing is, if you press your fabric the wrong way, you’ll cover up the magic arrow. That’s why I made such a big deal out of the placement of the fabrics.

Press the HSTs, once again pressing to to the background fabric.


Put the pieces right sides together and nest the seams as you did before. If you’re going to pin, now’s the time. When I do pin a seam intersection, I always pin the side that will go under the needle first. I don’t bother pinning both sides if the seam intersection. When I was first taught to quilt, she had us put a pin through the center of the intersection. This is about the only thing she taught us that I disagree with. I think if you put the pin through the point where the seams meet you’ll push them apart a little.


Sew the two halves together. See that magic arrow? The needle is lined up to pass a hair (a very fine hair!) outside the point.



Your pinwheel is finished! Except – if you pressed to the side that center intersection looks awfully lumpy. After all, that’s eight layers of fabric. No matter which way you press it isn’t going to lie flat.


So, split the difference! Clip that little chain that held the two pairs of HST units together. Gently slip out a couple of stitches in the seam allowance. You don’t have to pick them, just press one half of the seam allowance one way, and the other half the other way. It will be obvious which way the way to go. Wiggle the seams a little from the back until it opens up. Look at that! A cute little pinwheel on the back:


Press that little pinwheel flat, then press the rest of the seams. Flip it over, and there you go! (Please don’t mind Buttercup’s paw in this photo. She was getting pretty desperate for attention by this time.)


Check the block – it should now measure 6 1/2″. Because each of those HSTs were exactly the right size, your blocks should be pretty close to accurate.


Lay out your four completed Pinwheel blocks, making sure everything lines up properly as far as fabric placement.


Sew the four pinwheels together the same way you did the individual pinwheel blocks. You’ll even have a final tiny pinwheel on the back when you’re finished.


And there you have it! It should measure 12 1/2″ square.


So how did yours turn out? What do you think of half square triangles and pinwheels? After trying all four methods, do you have a favorite? Can you see how each method has advantages for certain types of projects? Do you have any recommendations (preferably with links) for other HST methods? Is there anything I didn’t explain clearly enough?

Are you still reading?!?!!

Whew. And for the record, it’s been exactly 3 hours. Boy, am I long-winded.



  1. Wow, you sure did put alot of time into this post and it shows. Thank-you. :0) I have always been frustrated with triangles and incredibly nervous to attempt a whole project that would include them. All the tips make complete sense, but I never would have thought of it all on my own. Can’t wait to attempt some triangles again and maybe even be successful!

  2. Thank you so much for taking the time to do this, it will certainly give me a guide to doing them properly. You wouldn’t think such a basic shape could come up with such a lovely pattern with just the right choice of material.

  3. I just checked your blog again after reading your initial “HST Advanced?!?” post and taking the survey. (I am one of those buy-on-sale people.)

    Your post really got me thinking about what I haven’t done and what I would like to learn. I got out a notebook and started making lists and jotting down ideas. I came up with a year long series of posts (weekly) starting with easy (log cabin) and ending with curves, applique and odd shapes (apple cores etc.). I would of course, bring in guests for things I know little about (like applique – I’ve tried it, but I am nooo expert!).

    I came back to tell you about my wonderful, totally unique idea – that of course you had already thought of. oops. Would you mind if I did it anyway? Could I link to some of your posts – I feel no need to reinvent the wheel, and this post is EXCELLENT! but I don’t want to steal your ideas. Anyway, drop me a line. 🙂

    • Leila, the more people encouraging quilters to try things, the better! I think it’s great that you had the same idea – in fact, Jeanne at Grey Cat Quilts was the one who first talked about it a couple of months ago, but she generously allowed me to run with it here because of the recent interest. You’re welcome to link to my posts, and if I’d love to link to yours as well.

  4. I am the one who adds the 7/8 inch to my squares and sews them into two HSTs, but I liked Jeannes method of doing 4 at the same time better still.

  5. Thank you for doing this series. I inherited a partially pieced quilt top from my Mother-in-law when she passed away a decade ago. I am finally trying to turn a pile of random squares into a quilt. I am really enjoying it, but I have SO many questions.

    Have you considered doing a post on the basic quilting supplies. I live in Malawi (south east Africa) and have no access to quilt stores at the moment. I will be home in the states this summer and want to buy some basic supplies. There seems to be a gadget for everything. My mother-in-law obviously used a cardboard template and cut each square by hand, with pinking shears, it’s making the idea of 1/4 seam allowance a bit challenging. I know I want a rotary cutter and cutting mat, but what size is best? Are there any other things I really should have? What is nice, but I can live without it? There is a limit to how much I can stuff in a suitcase, so I only want to buy what I need. As far as I can tell the rule is she/he who dies with the most toys (and fabric) wins. What is the least I can get away with?

  6. I noticed in one of the pictures in the post you have what looks to be a seam allowance guide on the bed of your machine. Could you please tell me where it came from? Thanks for your help!

    • Kathy J, the seam allowance guide I use is an early version of the Seamingly Accurate Seam Guide by Reanna Lily Designs. It looks pretty beat up on my machine because it’s several years old. I have the paper version that she originally made available in a PDF. She now has a much more durable adhesive version. Some day I’ll replace mine, but for now, I’m happy with it.

  7. Thanks for the info, I’ll check it out! I have been using a vinyl cling-sort of strip but it has a tendency to slip and is rather a pain. Again, appreciate your help.

  8. Interesting to have a detailed how to after disagreeing that pinwheels are intermediate. Thats a lot of steps and considerations to get those points to cross perfectly. As an advanced sewer in some areas, the pinwheel blocks I made didnt turn out so well and so I have to agree that the skills to do them well are basic, if you havent taken enough classes and practice to make that second nature then pinwheels are hard. Or any block with bias edges and many layers coming together in a point. Disliking how my peicing came out has headed me towards applique and foundation peiceing which come out better. Its also given me the realazation that some styles of quilting I like and some I dont and thats ok. So Ill make quilts that use the styles I can do well and take a couple more classes on peicing, and maybe grow to like it. But the whole debate about dumbing down quilting is kinda dumb itself. There are so many skill levels out there that its silly to quantify. What is annoying is the people who act like they have invented something new and that their way is the only way. Everything with fabric has been done before, it just gets discovered and popular again. All these “modern” quilters crack me up, can you say early 60’s? Theres nothing new or modern about this fad, just “everything old is new again”. Let it go people, just please yourself and dont pick on anybody else.

  9. I do appreciate the how to, Ill print it out and next time I do some pinwheels hopefully they will come out better with such excellent instruction, Thanks much!

  10. Awesome post! Thanks for the hard work of getting out there in an organized manner.

  11. Sandi, I had a problem with squaring up the block after sewing the triangles. The template kept slipping off the seam. I guess I should have pressed the seam open.

    • I also sometimes have trouble with the ruler slipping. There are several ways you can make your ruler more “grippy” – a product called OmniGrip (a clear static sticker that covers the entire back of the ruler), small sandpaper dots from the hardware store, or even a few quick dabs of rubber cement on the back of the ruler. Wait until it dries before you use it, of course!

  12. Dear Sandi,

    I found your blog during the brouhaha about dumbing down, and as a very new quilter whose tastes lean modern and whose education comes via internet and books, I wanted to say first, how much I admire the way you’ve addressed the responses to the various posts, and then to thank you, as enthusiastically as I know how, for this wonderful lesson. I just learned so much, so quickly, thanks to your generous series. I’m working on something with 45-degree triangles and you have just brought it so much closer to my reach. Thank you, thank you, thank you.

  13. I don’t know if I’ve actually seen someone press their pinwheels that way. I will have to try it – I get so frustrated with that huge lump I always end up with!

  14. Thank you for taking the time to write this tutorial. I’ll have to give it a try.

  15. This tutorial is absolutely amazing thank you so much. Maybe now I’ll actually be able to make one of these.
    Patti xxx

  16. This was really helpful, but I still didn’t quite understand what you were doing there in the center to get the many layers of seam allowance to lie flat. What “chain” were you clipping, for example? Did you clip through just one seam allowance, or through both layers? And where exactly were the stitches that you “slipped out”? In the very center of the intersection, or next to where you clipped the seam allowance? Since this took you three hours to put together, I hate to ask you to elaborate a bit more, but . . . I just don’t quite get it! Thanks so much.

    • BoiseNoise –
      The chain that I clipped was the thread that connected the two sections together as I was “chain piecing”. If you don’t chain piece, you won’t have a chain. You can see the chain in the photo named IMG_0558 about halfway down the page (the name appears if you hover over the photo). It’s the photo right after the Sneaky Little Quilting Tip. If you look really closely at the photo of the back of the block you can see a little loop of thread coming out of the center. I did not cut through any fabric, only thread. The stitches that slipped out were between the seam and the edge of the fabric at the center. Once you cut the chain, if you just wiggle the seam allowances and push them in the direction you want them to go, the stitches will slip out by themselves. Check out this photo on my Flickr page – hover over the photo to see the notes (look at them in order for instructions).

  17. thanks so much for that really helpful info about making the back sit flat – I just made a little half square triangle quilt and I wish I’d read your article before that – but at least I’ll know where to go next time 🙂 and that little teeny pinwheel on the back is cute !

  18. Thank you for the excellent advice! Just finished a quilt top with pinwheels and the seams were perfect! A first for me.

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