Beginning Quilting - Making Half Square Triangles | Madam Sew

Beginning Quilting - Making Half Square Triangles

Making Half Square Triangles is an essential skill in quilting. This method is quick and accurate, so your points always come out sharp. You’ll need two fabrics, a light and a dark, your rotary cutter and non-slip ruler, thread snips and an open toe foot.

Start by cutting your squares to at least 3/8" (and I do 1/2") larger than you want the finished half square triangle (HST) to be. In other words, if you need the HSTs to be 2-1/2 inches for piecing the next step, cut the squares 2-7/8 to 3 inches square. In the example, I’ll sew 4-1/2-inch squares to get a 4-inch HST, which will then finish in a quilt at 3-1/2-inches.

HST piecing is even more accurate when you mark the actual sewing lines instead of relying on sewing 1/4-inch away from a line.   To mark your sewing lines, place a ruler on the square, with the 1/4-inch line running diagonally from one corner to the opposite corner on your lighter color fabric.

Note the 1/4-inch line is on the point.

Draw a line at the edge of the ruler which will be 1/4-inch away from the center.

Flip the square and mark a second line the same way on 1/4-inch away from the center.

Pair the marked square with a second square right sides together. Most of the time this will be a focus fabric and the background fabric. Put the #29 Open Toe foot from the Madam Sew Ultimate Presser Foot set on your machine. This foot makes it easy to see your lines. Begin sewing on one of the lines. Sewing on the edge of the line nearest the center gives me a more accurate half-square triangle unit.

Chain piece by setting up all your squares, then running them one after another through the machine. As you approach the end of the first HST, place the next one in line with the first.

Continue sewing across the gap. Don’t worry, a few stitches without fabric won’t be a problem. It will create a little chain of thread between the pieces. Continue until you have all the squares sewn on one line.

The chain makes sewing the seam on the other side really easy as they are all together. Just turn the chain around and sew 1/4 inch away from the other side of the line.

When you get to the gap, just sew across like you did before and keep going. This makes the sewing go much faster than doing each one individually.

When you are done, you’ll have a chain of squares.

Cut the pieces apart from each other by snipping the little chain of thread between the squares. I love my Stork Scissors for this.

Then cut down the center from corner to corner between the sewn lines to yield two HST units with quarter-inch seam allowances using your rotary cutter and non-slip ruler.

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Press toward the darker of the fabrics.

Square your HST units to the correct size, placing the 45-degree line along the diagonal seam and trimming all four sides.

Trim two sides to the desired size, then turn the square to complete the trimming. Using a small ruler, like this one, you may need to turn several times. Just get the first cut accurate by aligning the 45-degree line on the sewn seam.

That's it! No need to be afraid of a lot of HSTs any longer. Quilts are so much more interesting with these angles as part of the design.

Now you can do all kinds of blocks! This pinwheel block is very popular, and is just four half square triangles.

Let’s look at sewing HSTs into blocks, there is one trick that you need to know. Sew this one nesting seams like you did in the first Beginning Quilting lesson using your Quarter Inch Foot to make your seam size accurate.

Then, press to the darker of the two sides, so you can nest the seams. Note that there is a quarter inch of seam allowance at the top of the points.

Now, pin your sections together, and note the little ‘X’ that has been created with the two previous seams.

Line up your sewing line to go precisely through that point. Using the quarter inch foot will make this easy.

Press the final block, and you have perfect points.

You can do flying geese this way too.

Or simply face the triangles opposite each other in rows.

Combine HSTs with the same size squares and you can get a Maple Leaf block, great for autumn inspired quilts.

Next time you see a pattern with a lot of HSTs, be confident, you can do it. In the coming weeks, we’ll do more basics and also begin to put things together for some fun designs, simple enough for beginners, yet fun enough for more advanced quilters to do as well.

Happy Quilting!


See my blog at for more patterns, tutorials, quilt alongs and ideas.

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Very clever way to make 1/2 square triangles xx


Thank you so much for posting your tutorial..maybe now I can finally make those half square triangles faster and straighter

Susie Percefull

Awesome, very helpful, Thanks.

Jeri Doucette

That was an informative article. I got some key tips on lining the points up everytime instead of just getting them “close”. Thanks.


Hi, I really liked your HST tutorial. It is very easy to follow along with and end up with what you are suppose to have!!

I would like to see a tutorial, and maybe you do already have one, a tutorial on squaring up HST were you leave them still folded in half and then you only trim 2 side. You are still using the 45 degree angle but with only those 2 sides. You are not repositioning the rule, so I feel that there is less room for error. Thank you.

Rene' Turchany

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