How To: Half Square Triangles (HST)

I love Half Square Triangles.  There are SOOOOOO many things that you can do with them!  I even like that they have their own abbreviation – HST.  They are pretty cool.

I once showed someone a quilt that I was working on with LOTS of churn dash and pin wheel blocks, both uses 4 HST each.  She, any many others, were amazed at all the little pieces in the quilt.  I often would explain that I did not cut hundreds of little triangles and sew them together – I made half square triangles the fast way.

There are a few ways of making them the “fast way.”  You can make 2 at a time, 4, 8 or even more!  I am going to focus on making 2, 4 and 8 at a time on this tutorial.  The dozen at a time will come on another post.

The best way is to start with squares of fabric.  I had some left over 5″ squares from the Red, White & Blue Stars Quilt – you can read about the quilting in this link: How to: Stitch in the Ditch Quilting.  I made only half square triangles using the 4 method and arranged them into stars.  Here are my left overs, they are from an American Made Brand pre-cut pack.Half Square Triangles fabric1I then take 2 squares and pair them up.  Below just shows the two but they need to be right sides together and directly on top of each other.  I love how solids do not have a right or wrong side – both are the right side!Half Square Triangles fabric2

2 at a time

The method used to make 2 HST at a time begins with drawing a straight line diagonally down the square.Half Square Triangles 2 - line

Then sew 1/4″ away from that line on both sides.  I used white thread throughout these examples so it can be seen easily.Half Square Triangles 2 - sew

I like to press after this step.  Next you cut right ON THE LINE.  Note how the 1/4″ dotted line on my ruler is on top of the sewn line.

Press open.  I press to the dark side.  It is best to cut off the little “wings” that hang over the edges.Half Square Triangles 2 - finished


4 at a time

Use the same method of starting with 2 squares – right side together and directly on top of each other.  No need to draw any lines.  Sew 1/4″ on all 4 sides of the square.  (Sometimes pre-cuts have a pinked, or jagged, edge as shown.  Just pick which side of the edge to sew from and stay consistent.  I chose from the inside edges of the pinked edge.)Half Square Triangles 4 - sew

I press all seams at this point.  The flatter the square the better it will turn out.  Cut diagonally, both ways, from corner to corner.  The more precise the cut the more uniform all 4 half square triangles will turn out.

The finished set of 4, after pressing open.Half Square Triangles 4 - finished

8 at a time

Begin again with 2 identical shaped squares, right sides together and directly on top of each other.  Draw a line from corner to corner, diagonally.  This time draw 2 lines making an “X.”  Sew 1/4″ from each line on both sides.  See my little bobbin outage there on the left?  I need a flashing “bobbin out” sign!Half Square Triangles 8 - sew.JPGAgain, I press all my seams here.  Cut directly on the drawn line in both directions AND halfway into the square making a “+” sign.  This will result in 8 triangles.

Press open all 8 half square triangles.Half Square Triangles 8 - finishedCheck out just 2 of the interesting blocks that could be made using these 8 HST.


There are “magic charts” and sizes to make the perfect sized HST using these methods and once I can find the charts I will post them here.

I hope this helps and makes you want to make MANY half square triangles of your own!  Which is your favorite method?


One comment

  1. […] Next is a quilt I started with my second son in an attempt to get him interested in quilting.  I wanted him to enter it in our local Adams County Fair.  I found a great pre-cut called Military Max, I think, and ordered a few in the 5″ size.  I showed him the fabrics and let him pick a design he liked.  He just wanted simple pin wheels with a cool border.  He sewed a few and was bored.  I decided to take over.  This is how far we got but used the method How To: Half Square Triangles (HST)  […]


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