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.

Half-Square Quilt Fabric

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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 to your 3” measurement, 7/8”.  (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.

Fabric Square for Making Half-Square Triangle Blocks

Step 2:

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

Marking Fabric for Half-Square Blocks

Step 3:

With right sides together, draw two diagonal lines corner to corner.

Stitching Fabric Blocks

Step 4:

Stitch a quarter inch of either side of both drawn lines.

Step 5:

Carefully cut apart with out shifting the stitched fabric square.

There will be four cuts:

Cut 1: Vertical cut right down the center.

Cutting Fabric Square - Halving

Cut 2: Cut down the center horizontally.

Cutting Fabric Square - Quartering

Cuts 3 and 4: Cut on both the drawn diagonal lines.

Voila! Here's a look at some pinwheels made using the Magic 8 method.

Close-up on Pinwheel Design Using Half Squares

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!

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

Pinwheels and Tree Quilt - Craftsy Member Pattern

Poppa's Tree Farm Quilt

Switch up the colors, and this lovely tree quilt can be enjoyed not only at Christmas, but all year round. This can easily be made into a wall hanging, too!

Get the Poppa's Tree Farm pattern.

Valentines Quilt & Pillow - Craftsy Pattern

Pinwheel Table Treat & Pillow Kisses Mini Quilt

The small scale pinwheels on this sweet little mini quilt are a breeze using the Magic 8 method.

Get the Pinwheel TableTreat & Pillow Kisses pattern.

Hot Coco Mug Rug with Pinwheel

Hot Cocoa with Friends Mug Rug

These quick and easy wool appliqué mug rugs made with traditional Friendship Star blocks are perfect for enjoying a hot cup of cocoa with a friend. Super yummy!

Get the Hot Cocoa with Friends Mug Rug pattern.

Quilt Featuring Half Squares - Pumpkin Spice Pattern

Pumpkin Spice Quilt

This quilt is a great stash buster! Warm it up for winter by adding a flannel backing. So snuggly and easy to make!

Get the Pumpkin Spice pattern.

About the author

This post is written by quilting blogger Karen Walker of Laugh Yourself Into Stitches. Karen has been a quilter for the past 15+ years. She enjoys making quilts, has a longarm quilting business, and recently became one of Craftsy’s indie pattern designers. She uses this Magic 8 method in almost all of her quilt designs.

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Genius Hacks Every Quilter Should Know

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Kimaley Whitsett Johnson

I can’t wait to try this method!

Delphina Martinez

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

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.

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

Jean Eversole Lorenz

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

Madge Mason

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

Terrie Durgin

This is great! Thanks for sharing the tutorial 🙂

Terrie Durgin

This is great! Thanks for sharing the tutorial 🙂

Kathleen Dober

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

Brenda Sarrasin

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


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.


it would be ⅞ to each one…
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…


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

KimandDennis Bemis

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


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

Lorry Meyers Kirschner

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

Lorry Meyers Kirschner

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


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


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?

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.

thanks for your question!


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

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:


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.

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!!


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 ?
(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…



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

karen walker

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.


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


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


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.


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.


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