Easy Half Square Triangle Quilt Tutorial

Half square triangles are one of my favorite quilt blocks to work with!  They are easy to make, incredibly versatile in layout, and are equally as fantastic in small and large sizes! Continue reading to learn how to make a quick and easy half square triangle quilt, this tutorial is perfect for beginners and experienced quilters alike.

This quilt grew out of the plaid fabric in navy and mint, with additional navy and mint added in to get enough yardage.

Half square triangle quilt blocks start with two squares of fabric.  They can be made in any size, and the math for figuring out the size to cut your square isn’t too hard.

Sizes of Blocks

Whatever size you want your finished block (finished means once it is sewn into the quilt and has no raw edges remaining), add 7/8” and you’ve got the size you need to cut!  (On a quilting ruler, 7/8” is the last little hash mark before the next inch.)

If you are planning to follow this tutorial as if it is a pattern, I cut my squares 5 7/8” and I cut 120 squares.  My quilt will finish at 50” wide by 60” tall.  You can make your squares whatever size you want and/or need, and you can use as many or as few of them as you want. 

The first half of this tutorial is how to make half square triangles.  The second half is how to place half square triangles to make the quilt top that I made.

How to Make a Half Square Triangle Block

Using a pencil (or a pen- it won’t be visible in the finished quilt) draw a line from one corner of the square to another, across the diagonal.

Place two squares together, right sides together.  The square with the pencil line on the diagonal should be the square on the top of the pair.

Sew ¼” from the pencil line, on the right side of the line.

Trim the threads, and sew ¼” on the other side of the line.

There are now two parallel seams, ½” apart, with the pencil line right down the middle.

Use the rotary cutter and ruler to cut on the pencil line.

You’ve now got two blocks.  Here is a zoomed in view.

There is no need to stop in between each block.  Half square triangles are perfect for chain piecing.  You get a nice, tidy pile of pieces folded up behind your machine, and it saves both time and thread!

This next picture shows part of what I like so much about HSTs.  This picture is after both seams have been sewn, but before it has been cut.  Finger-pressing the seam open shows just how little of the fabric is lost to seam allowance.  Some quilt patterns have lots and lots of fabric eaten up by the seam allowances.  There is nothing wrong with that, it just means more fabric yardage is required for a quilt that finishes at the same size.  I like that HSTs don’t eat up a lot of fabric.

Now that you’ve sewn and cut your squares, iron the seam, pressing towards the darker of the two fabrics.  Every pair of squares makes two HSTs.

Since this is such a quick quilt block to make, you end up with a huge stack of them finished and ready to make a quilt top in a hurry.

So now that you know how to make HSTs, you can make a huge variety of quilt blocks and quilt tops.  Continue reading if you want to make a quilt top like mine.

How to Make a Half Square Triangle Quilt Top

Three different combinations of ways to lay out half square triangles make up this quilt.

HST Block 1

First, a block in which the triangles make up a diamond within the square.  I’ve added black lines to help you see how the seams from the HSTs make the diamond.

Star by laying out four HSTs, turning them so that the seam creates a diamond within the larger square.  Sew the top two together and the bottom two together, alternating direction.

You now have two pairs, return to original layout (to make sure you are sewing the correct edges together- no backwards mistakes here!) and sew the top pair to the bottom.

And now you’ve got a diamond within a square!

Make one.

HST Block 2

Second, a block in which the triangles make arrows or points. 

As in the previous block, layout four HSTs, turning to achieve the desired fabric placement and to get the arrow points.  Sew the top two and then the bottom two.

Sew the resulting pairs.

Now you’ve got a block with perfect, crisp points!

Make nine.

HST Block 3

Third, a block in which all of the half square triangles are angled in the same direction.

Again, four HSTs, this time you are turning them so that all four blocks have the seam point up and to the right.  Sew pairs.

Sew the pairs into a block.

The finished block.

Make 20.

Now that you’ve got all these beautiful blocks, to make the blocks into the quilt top, start with the first block, the one that makes a diamond within the square.  Surround it with 4 of the blocks that look like arrows, each pointing away from the diamond.

Add one more arrow to the top, and two more arrows to the right side and the bottom.

Start filling in the rest of the quilt top with the third blocks, the ones that all seams point the same direction.  These blocks can be turned any direction, to match the direction of the seams in any of the four quadrants of the quilt top.

Now you’ve got your quilt top all laid out, and are ready to sew the blocks into rows, and the rows into the quilt top!  Isn’t it pretty?

If you have a four legged helper, work quickly, otherwise your hard work may end up like mine:

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And, voila!  A finished quilt!  Mine measures 50” by 60” and has a flannel back and stripy binding. 

I quilted ¼” inside and outside all of the diagonal lines, to help the pattern to POP!