Quilting Blog

How to Make 8 Half-Square Triangles at Once: The Magic 8 Method

If you don’t like cutting and stitching loose triangles together on the bias, or need to make lots and lots of half-square triangles for a quilting project, here’s a quick and easy solution.

Magic 8 Half-Square Triangles

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Making the Magic 8 work for you

Step 1:

To make a Magic 8, first determine what size finished half-square triangles are desired.

For example:

  1. Let’s say you want to make 3” finished half-square triangles.
  2. Add 7/8” to your 3" measurement  (Your total is now 3-7/8”)
  3. Multiply your total of 3-7/8” by 2. (That equals 7-3/4”)
  4. 7-3/4” squares are the size needed to make your 3” finished half-square triangles.

Step 2:

Cutting Two Squares to Make Half-Square Triangles

Cut two squares the desired size based on the formula above.

Step 3:

Drawing Diagonal Line on Fabric Square

Place the two squares on top of each other, with right sides together. Then, on one of the fabrics, raw two diagonal lines corner to corner.

Step 4:

sewing for magic 8 hst method

Next, you'll stitch a total of four lines: 2 on both sides of each diagonal line, ¼" away from the line.

Step 5:

Now, you can carefully cut the sewn square into the eight HSTs. You'll make a total of four cuts.

Cut 1:

Cutting Fabric Square in Half Vertically

Cut vertically right down the center. Align your ruler with the center where you drawn lines intersect and one straight edge of the fabric squares.

Cut 2:

Cutting fabric square horizontally

Make a second cut that's perpendicular to the cut you just made. At this point, it's best to leave the fabric pieces where they are — don't try to rotate the fabric! Instead, walk around your table so you are better positioned to make the cut, or turn your cutting mat.

Cuts 3 and 4:

cutting fabric square diagonally

Cut on both of the drawn diagonal lines, between your stitching lines. Again, it's best not to move your fabric; instead, move your body or your board so that you don't shift the fabric.

Step 6:

Separating half square triangles

Now that you're done with your cuts, you can separate the cut pieces...

finger pressing a gray and purple half square triangle

...and open them up to reveal your perfect half-square triangles! Press the seams to the darker side and you're ready to use them in a project.

Use the Magic 8 method to whip up these fun quilt patterns!

Half-square triangles are often used in many quilt blocks and quilt patterns. Pinwheels, charm quilts and many star blocks to name a few. Just imagine how this simple and fast Magic 8 method will change your quilting life!

Carpenter Star

Carpenter's Star Quilt

These striking star quilts are typically made with tricky Y-seams, but this genius variations achieves the same style with only half-square triangles and squares.

Get the FREE Pattern

HST Table Runner

Modern HST Table Runner

Because this table runner only uses two colors, it's the perfect contender for the Magic 8 method. We love this striking off-center design, but it would be easy to put your own spin on the arrangement.

Get the FREE Pattern

HST Baby QUilt

Half-Square Triangle Baby Quilt

A kids' fabric would make this baby quilt extra sweet, but it would also be a great pattern to use up coordinating 6" square scraps.

Get the Pattern

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Genuis quilting hacks

Want 18 pages of helpful hacks every quilter should know?! Download our E-guide to save and print. Download FREE PDF »

35 Comments

Kimaley Whitsett Johnson

I can’t wait to try this method!

Reply
Delphina Martinez

If I want a finished six inch pinwheel what size square do I start with.?

Reply
Beckie Orlando

To make a 6-inch square pinwheel, I think you start by doing the math:

6 inches + 7/8 = 6 7/8 x 2 = 13 3/4 inches
For decimals use:
7/8 in a decimal is .875. So 6 + .875 = 6.875 x 2 = 13.75 which is 13 3/4; then cut your 8 triangles as indicated in this tutorial and sew together.

Reply
Wilma Mulder

For a FINISHED 6 inch square pinwheel, you need 4 HST`s. Finished 6 /2=3 inch finished = 3.5 inch HST, follow calculations 3.5 inches + 7/8 inch = 4.375 x 2 = 8.75 inches square to start with

Reply
Jean Eversole Lorenz

I have used Karen’s turorial and made magic 8 half square triangles. So fast and accurate.

Reply
Madge Mason

I am definitely going to try this for my next Pinwheel quilt. Thanks so much!

Reply
Terrie Durgin

This is great! Thanks for sharing the tutorial 🙂

Reply
Terrie Durgin

This is great! Thanks for sharing the tutorial 🙂

Reply
Kathleen Dober

Thanks for sharing I have lots of material and scrap peices will try real soon.

Reply
Brenda Sarrasin

if you add 7/8″ for finished 3″ blocks, what is the formula for larger ones please?

Reply
Lois

You add the 7/8″ to any size square you want to make…3″, 5.25″, 8.5″. Any size, when you add 7/8″ and then multiply by two you will end up with what size squares you need to cut to start the process.

Reply
eva

it would be ⅞ to each one…
example:
for a 2″ finished HST…you’d cut a 2⅞” set of squares
for a 4″ finished HST…you’d cut a 4⅞” set of squares
for a 5″ finished HST…you’d cut a 5⅞” set of squares
for a 6″ finished HST…you’d cut a 6⅞” set of squares
for a 7″ finished HST…you’d cut a 7⅞” set of squares

and so on…

Reply
Chrissy

Eva, you left out “then multiply by 2!”

Reply
KimandDennis Bemis

Where was this method when I was struggling to figure out how to make a flying geese for my grandsons quilt. 🙂

Reply
Karen

Flying geese are made differently. Google an Eleanor burns tutorial for geese.

Reply
Lorry Meyers Kirschner

Yes…what a game changer this process is…woohoo, can’t wait to do this!

Reply
Lorry Meyers Kirschner

Yes…what a game changer this process is…woohoo, can’t wait to do this!

Reply
margaret

What an absolutely wonderful method! Stash the ones you do not use and make something unusual and original.

Reply
Patricia

I need a 2″ hst. Added 7/8 to the 2″ which made it 2 7/8. Then multiplied by 2. Equals 5 3/4″ square.
The finished product was much larger than 2″. What is the correct formula?

Reply
karen walker

Hi Paticia…i’m sorry i am just seeing your comment. With your listed measurements, you will get a
2-1/2″”UNfinished half square triangle. Finished triangle will measure 2″.

Go here to download my free Magic 8 pdf which includes a cutting chart.
http://www.craftsy.com/pattern/quilting/other/free-magic-8-tutorial/99550

thanks for your question!
~karen

Reply
Sharon

Do you always add 7/8″ to any size finished square or does it change with the size?
Any help would be great!
Thanks, Sharon

Reply
karen walker

Hi Sharon,
Adding 7/8″ to your squares will result in a FINISHED half square triangle measuring in even inches, ie: 1″, 2″, 3″, etc. If you add 3/8″ to your beginning squares, the FINISHED hst will measure in half inch increments, ie: 1-1/2″, 2-1/2″, 3-1/2″, etc.
If you are on Pinterest, you will find a number of different charts for a variety of quilting formulas here:
https://www.pinterest.com/chezstitches/quilting-formulas-and-tutorials/

Thanks!
~karen

Reply
Karen Scribner

Please remove this comment. It is very confusing, especially to new quilters who do not understand math, and the concept of a block that is finished, versus unfinished that has the 1/4″ seams showing.

Reply
Sue Hills

Before seeing the above comments I tried this formula and the HSTs came out too big. I reduced the size of the starting squares and tried again. Still too big. I need a 3.5″ HST so that when I sew 4 together I get a 6.5″ pinwheel block. I now see from the comments above that it is a different formula for a finished HST measured in half inch increments. It would have been useful if that had been explained in the tutorial. Surely most blocks are a rounded size and therefore need a half inch added for the seam allowances when sewn together meaning they will always be a something and a half finished block? I’m glad I read the comments as I was giving up the will to live!!

Reply
allyn

can some one PLEASE tell me where to find the chart for these measurements. .
ive been on and around the website for about an hour now and i cant find it or the download (link takes me to identical page, without comments).
im (a newbie) trying to make a finished HST measuring 1 1/2″.

(1 1/2 + 7/8) * 2 = 4 3/4 ?
or
(1 1/2 + 3/8) * 2 = 3 3/4 ?

i cut out all of my 1 1/2″ finished squares.
then cut an extra 10 and cut them if half to make my 1 1/2″ HST.
i hope 1 day i will find a use for them…

thanks
allyn

Reply
allyn

getting a little toooo flustered with this…
squares are 1 1/2″ UNfinished.
therefore, a 1″ finished hst would =
(1 + 7/8) * 2 = 3 3/4

Reply
karen walker

Allyn,
I should add that the link i provided in my comment above, has the same picture of the half square triangles as seen at the top of this blog post…maybe that brought some confusion. However, you can click on the Download Digital Pattern for a free pdf tutorial.

Reply
Alex

I literally just finished cutting a whole bunch of triangles and now I am so angry for not finding this page first!

Reply
Melanie

HST are currently driving me CRAZY!!! I am working on a Bear Paw and one block has 16 HST LOL

Reply
Karen

I made absolutely perfect 1/4″ seams with my Janome 1/4″ foot on cheap (practice) fabric. My squares were about 1/8″ too small. It may have been because I cut the squares first, then steam-pressed them. They may have shrunk that much. Nevertheless, I would recommend cutting the big squares just a tiny bit large OR taking scant 1/4″ seams and then trimming the HSTs to perfection. I love the concept anyway. :>) Thanks for sharing it.

Reply
Jan

I really do not understand the added “?/8″ ….why not just add 1/4” to each side instead of fulling around with the ?/8 “? When ever I cut a pattern piece, I naturally just add 1/4 ” seam allowance.

Reply

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