Half Square Triangles HST


“Half Square Triangles” and “Quarter Square Triangle” are important for quilters. They should not be a mystery.

> > > The only difference between an HST and a QST is the straight grain.


These Inklingo triangles are both daffodil-colored (see below) and identical in size, but the straight grain is different.

For HST, the straight grain is on the two short sides. For QST, the straight grain is on the long side.

It’s that simple. No mystery.



Monkey says understanding HST and QST is VUI (very useful info, LOL).

Quilters want to have straight grain on the outside edges of quilt block and quilt tops whenever humanly possible.


Q. These triangles are used in many ways, not necessarily sewn into squares (Sawtooth Squares), so why are they called Half Square Triangles?

A. Because in the olden days (pre-Inklingo), quilters cut squares in half on the diagonal to get two at a time.

See the free Triangle Tips PDF on the Inklingo web site under the Machine Piecing tab.


If you learned how to make triangles the old-fashioned way, before Inklingo, you are familiar with adding 7/8 inch to the measurement of a square to cut Half Square Triangles.

Whenever possible, pattern designers use HST which are easy to measure. They like to avoid measurements in eighths. For this reason, a pattern may require you to cut a strip 3.5 inches wide, then cut the strip into 3.5 inch squares, and then cut the squares in half diagonally.  In that case, the FINISHED size of each triangle is 2.625 inches (2-5/8 inches).

It is ironic that because of the “olden days way” of cutting HST, when designers want to avoid asking a quilter to measure and cut eighths of an inch, the finished triangles end up being in eighths.

Why do you need to know about 7/8?

Inklingo quilters don’t have to measure or add 7/8 any more, because all Inklingo shapes are named with the finished size.

However, if you are using a pre-Inklingo pattern, this info will help you determine the finished size of the triangles, if it is not stated.

7/8 = 0.875

To avoid the math, tell designers you want their patterns to identify the finished sizes!!

Working backwards, if a pattern requires you to cut a square on the diagonal for two triangles, if you subtract 7/8 (0.875) from the size of the square, you know the finished size of the HST triangles.

The new Inklingo Half Square Triangle Shape Collection includes 12 different sizes which would traditionally have been cut from squares 1.25, 1.5, 1.75, 2.0, 2.25, 2.5, 2.75, 3.0 3.25, 3.5, 3.75, 4.0 inch—very common sizes.

More shapes and sizes are added every few weeks. Check the Inklingo Index of Shapes (under the Support tab) to find the shapes and sizes you need.


Printing triangles on fabric with Inklingo is

  • faster
  • simpler
  • more accurate

That’s a beautiful thing.

Printing the shapes on fabric is another beautiful thing:

  • No measuring
  • No math
  • Just print one of the two fabrics (usually the lighter one)
  • No tricky tools
  • No paper to pick off
  • Correct straight grain
  • Sew bias seams before they are cut
  • Precision corners
  • Cut with scissors or a rotary cutter

With Inklingo, you just need to know the finished size and where you want the straight grain, so the question is . . . . Half Square Triangles or Quarter Square Triangles? HST or QST?

Now you know.

The daffodils are blooming in our back yard. Spring is here!

Linda & Monkey

PS Don’t forget to leave a comment HERE to have a chance to win a $25 Gift Certificate on Mother’s Day!


New to Inklingo? Order and download free shapes and start sewing in the next few minutes. Quick Start  (Always FREE.) There are triangles, diamonds, and squares  in the free collection—great for dozens of different blocks.

8 thoughts on “Half Square Triangles HST”

  1. It’s been a while since I did any sewing/quilting, but things are starting to calm down for me. You have provided us with another fantastic quilting tool! Thank you!!!

  2. But I love Math! I even love fractions. I must be so old fashion, at least that is what NeNeTurtle says. I just hate cuting eighths, the rules often move that much. Ick! Thanks for creating Inklingo. Sheron in the middle of the Mitten, where the Spring Beauties are bloom making it look like I live on a cloud of pink.

  3. Great info, Linda and Monkey. I have shied away from triangles in general because of all the squaring up and math involved in doing them. Thanks for taking on the hard part and giving us the easy part to use. I will keep this for reference.

  4. VGI…very good info from you and Monkey. Maybe one day designers will list the info of finished sizes of the parts but I bet it will be a long time coming as designers will want to please the most customers who are used to thinking in 8th’s of an inch!
    I personally add 1 inch and square up but I can see this would be much more efficent and no extra squaring up afterwords.

  5. Great info Linda! The 7/8 formula really helps in working backwards for all those quick-cut patterns out there.

    Maybe you know this answer too: If I want to sew a HST to a side of a square, and I know the size of the side of the square (say, 2″), and I know that the diagonal of the HST has to be 2″ (duh!), what is the finished size of the HST going to be? Is there a formula for that?

    The mind boggles what you can do!

  6. Great info, Linda & Monkey. Thank you for always making it so simple. I am so conditioned to think fractions– now I must re-tool my brain to think “decimals” so I will choose the correct collection to use.
    Perhaps this old dog can learn new tricks. Meanwhile I just keep a calculator handy and make “crib notes” in my Inklingo binders.
    Cyn; -)

  7. This is a great post to print out and keep in a notebook with other quilt-related VUI! I love using the HSTs and QSTs. While sitting at the hearing today, I was designing quilts in my mind using more HSTs and QSTs.

  8. Great lesson and clarification. I will definitely bookmark this page. Thank you for taking the math and confusion out of HST and QST. AND thank you for the new collection!


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