How to make an hourglass quilt block

UPDATED 12/5/23 - Hourglass Quilt blocks seem like an intimidating little block, but it’s as easy as making a half square triangle…times two! Let’s walk through these together!

First - what’s the difference between an hour glass quilt block and a quarter square triangle block? Well, it’s essentially the same thing! The block is made up of 4 quarters, these are 4 triangles that make your quilt block. These blocks can be made in a few ways, with 2 fabric options or even 4 options! The hourglass block is typically made with 2 fabrics, to give the hourglass look in the middle of the block.

So let’s get started!

half square triangles

Start with 2 squares the same size. For maximum impact, make sure that your fabrics are contrasting enough, otherwise, depending on the type of project you are making, the “hourglass” shape can get lost.

Want the easy Hourglass Quilt Math?

Starting Squares = Hourglass Block Finished Size + 1 1/4”

If you’d like a little more room for trimming, add 1 1/2” instead.

I am starting with (2) 5″ fabric squares. If you know how to make a 2 at-a-time half square triangles, then you are golden for the first part of this process! If not, bear with me while I explain how to make this valuable little block!

Do you need more help with making half square triangles? Check out my blog article and tutorial. Also, don’t miss my FREE downloadable Ultimate Half Square Triangle guide!

Use a pencil or fabric marking pen (I LOVE Frixon pens which disappear with heat from your iron) to draw a diagonal line across the back of one of your fabric squares. Match with the other fabric square and place right sides together. Pin if you would like.

Sew ¼” away from either side of the drawn line. Cut the squares apart along the drawn line. You will have (2) half square triangles. Important step here….Do NOT trim the half square triangles at this point! Press to set your seams and then press to the darker fabric.

Transforming our Half Square Triangles into Quarter Square Triangles

Now for the interesting part! Place the (2) completed half square triangles right side together, making sure the opposite fabrics are facing each other. Carefully line up/nest your seams and pin in place.

Matching up one corner and nesting these pretty seams

When nesting my seams for a quarter square triangle, I like to start on one end, nest my seams and pin, then peek at the center lines and make sure those are lined up and pin, then match your last corner and pin. Peek-a-boo…take a look at that center and make sure the seams are nested and lined up as well!

Use a pencil or fabric marking pen to draw a diagonal line across the back of one block. This line will cross the original seam of your half square triangle. *You can also do this step before lining the blocks up if you prefer. And now sew 1/4″ on either side of this drawn line!

You guessed the next step I bet…cut on the drawn line to reveal your 2 triangles. Now get ready for the magical reveal…but first…

Trimming

We need to do a little trimming! I discussed this in my 2 at a time half square triangle tutorial. The concept is the same, you have 2 methods of trimming your square triangles.

First, you can use this nifty trimming tool that is one of my all time favorites – the Clearly Perfect Slotted Trimmer. This makes trimming half square triangles and quarter square triangles SO easy! Simply line up the dashed line on the ruler with your sewing line and trim on both sides. The ruler also has nifty notches in the bottom that trim your dog ears off for you as well. If you are using this trimming method, after trimming, you will trim, open up your creation to reveal a beautiful hourglass block, and then press your seams open (of course you can press to one side but it reduces bulk if you press open).

Now for the second trimming method. Open up your beautiful block and press seams open (or to one side). Let’s stop for a moment and appreciate this beautiful center point! 

Using any quilting ruler that you may have, find the diagonal line and match it up with the diagonal line on your block. I am trimming my quarter square triangles to 4″ and because we want to clean up all 4 sides of the block, I am trimming a little bit off each side.

Line your ruler up with the diagonal line and trim. Then rotate your block and repeat. You can see that I have also lined up the center point of this particular ruler as well as the diagonal line. Trim again. Now we have a perfectly trimmed hourglass block! Beautiful!

Another look at these beautiful points! Even though I despise pinning sometimes, I really believe that pinning on the edges and near the center keep your fabric from shifting after you line up and nest your seams. 

Now we have 2 beautiful hourglass (quarter square) triangles!

Don’t forget to download your copy of the Double Cocoa Stars Quilt Pattern!

Want help with making your Half Square Triangles? Grab my Ultimate Half Square Triangle Guide.

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