How to Sew a Basic Hourglass or Quarter Square Triangle Block

Posted by Elaine Huff on

The Hourglass quilt block goes by several names – quarter-square triangle is a more common one. It starts out as a half-square triangle patch so the first part of this tutorial is much the same as my post on that subject. You can see that post by clicking here.

The Math:

The math behind how to figure out how big to cut the squares is pretty easy. Add at least 1.25″ to the size you want the finished patch to be. So if your finished patch is to be 4” square, cut the squares at least 5.25″ square. I prefer to cut the squares 1.5” larger, so that I have more wiggle room when trimming the resulting patch. So a 2” finished patch would start with two 3.25” or 3.5” squares, 4″ finished patch would start with two 5.25″ or 5.5″ squares, etc.

My finished hourglass patch will measure 3.5″ square so I started with 5″ squares. (Not the best choice – what can I make with 3.5″ squares?)

hourglass quilt block

Sewing Directions:

Step 1:

Match the two fabric squares right sides together.  Mark a diagonal line from corner to corner on the back of one of the squares.

hourglass 1

Step 2:

Sew a ¼” seam on both sides of diagonal line and cut along the diagonal line. You will have 2 half-square triangle patches.

hourglass 2

Step 3:

Open up both of the units and press seam allowance toward the darker fabric. Don’t square up the patches yet!

hourglass 3

Now here is where we add more steps.

Step 4:

Match the two half-square triangle patches, right sides together, and rotate one of the patches 180 degrees so the colors are opposing each other and the seam allowances nest together nicely.

hourglass 4

Step 5:

Mark a diagonal line on back of the patches perpendicular to the seam line. See how I’ve lined up the 10″ line on the ruler with the seam line? Since I’m not a perfect piecer, this is more accurate than drawing a line from corner to corner.

hourglass 5

hourglass 55

Step 6:

Sew ¼” (or a little less) on both sides of the diagonal line.

hourglass 6

Step 7:

Cut on the diagonal line.

hourglass 7

Step 8:

You will have 2 Hourglass patches. Press seam allowance. You can also tweek where the seam allowances meet on the back like I showed in the tutorial on the four-patch. You can click here to see that tutorial. This helps the patch lay flatter.

hourglass 8

Squaring Up:

Step 9:

Place the diagonal line on a square up ruler along one of the seam line of the patch. Since my finished patch will be 3.5″ square, I want to square up this patch at 4″ so I want a little bit of fabric showing to the top and right sides of the ruler and at the 4″ marks. Trim the right and top sides with a rotary cutter.

hourglass 9

Step 10:

Lift the ruler up, turn the patch 180 degrees, and line up the diagonal line of the square up ruler with the seam line. This time I’m going to match up the left and bottom sides of the patch with the 4″ marks on the ruler and trim the right and top sides of the patch with a rotary cutter.

hourglass 10

hourglass 11


Of course there are lots of variations of this patch – you can use 4 different colors and get mirror image patches,

hourglass 12

Or use 3 different colors to get this effect.

hourglass 13

The Hourglass quilt block also makes a good alternating block. I hope you've enjoyed this tutorial.

Happy Quilting!


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