The Two-at-a-Time Quarter Square Triangles (QST) Calculator

What’s the Math for Two-at-a-Time QSTs?

Before you start, you’re going to need to know two things:

  • The Finished size of your QST (that’s the dimension once it is all sewn together)

  • Whether you want to be exact or have a little extra fabric to trim down to size

The “Exact” QST Formula

If you're making QSTs Two-at-a-Time, you'll need two (2) same-size squares of different fabric. The "official" math (or what I call the in-a-perfect-world-where-I-don't-make-mistakes math) states that you add 1¼" to your desired finished size QST.

Finished QST Size + 1¼" = Starting Square Size

The “Oversized” QST Formula

I always trim my QSTs down to size (and I assume you do too): to factor in a little extra room for trimming, just add 1½" to your finished size and you'll be good to go!

Finished QST Size + 1½" = Starting Square Size

How to Make Two-at-a-Time HSTs Step-by-Step

"But, how do I make QSTs Two-at-at-Time?" you ask? To start, you are going to need two (2) squares of fabric (measuring the “Starting Square Size in the calculator above).

Step 1: Draw a diagonal line on the back of one of your squares

Step 2: then place it on top of the other square right sides together

Step 3: sew a ¼" on either side of the line then cut along the drawn line and press

Step 4: on the back of one HST, draw a diagonal line perpendicular to the HST diagonal seam

Step 5: place the HST on top of the second HST, right sides together, making sure the HST seams are parallel to each other

Step 6: sew a ¼" on either side of the line then cut along the drawn line

Step 7: press and trim down to size as necessary (to the “Unfinished” size in the calculator above.

What About Other QST Layouts?

Want to make QSTs with four fabrics? Easy! Just double the above recipe by two and start with four squares of fabric instead of four (and/or make sure to check out the Four-at-a-Time QST Calculator).

Want to make a “Split” QST (it’s a QST/HST hybrid!) with two fabrics or three fabrics? Make sure to check out that calculator as well!