Half-Square Triangles 12 or More at a Time
When you need twelve or more identical HSTs, it is less tedious to make them all at once, rather than 2, or even 8, at a time. This is simply scaling up the system of making them 8 at a time. You can also use this method to do the first step of multiple QSTs, because the first step of making QSTs is to make HSTs. There will be a difference in the math, depending on whether your ultimate goal is to make HSTs or QSTs. This method will result in HSTs in multiples of 4 (12, 16, 20, 24, 28, 32, etc.)
In this method, you can either draw your grid directly on your fabric, or you can draw your grid on paper. Personally, I prefer to draw my grid on paper, as the fabric is hard to keep from stretching and distorting when you are drawing that many lines. My preferred paper is graph paper with a ¼" grid, as that means that most of the measuring and making of exact 90° angles is already done for me.
There are some commercial pre-printed interfacing available that would serve the same purpose as drawing your own paper grid, but I don’t use them. With the pre-printed interfacings, you would have to purchase the correct size grid, and then if you later need to make a different size of HSTs, then you would have to purchase a different size grid.
I also recommend that the largest size pieces of fabric that you use are Fat Quarters, as if you use larger pieces of fabric than that, it can get a bit unwieldy under the sewing machine. If you are making smaller HSTs, you can make more of them out of a couple of Fat Quarters than if you are making larger HSTs.
Math:
- For HSTs, add 7/8" to the desired Finished size of the HSTs.
- Example: You need 3" Finished HSTs. 3 + 7/8 = 37/8.
- The measurement you need to remember is 37/8".
- For the first step of QSTs, add 1¼" to the desired Finished size of the QSTs.
- Example: You need 3" Finished QSTs. 3 + 1¼ = 4¼.
- The measurement you need to remember is 4¼".
- To figure out how many grid squares to draw:
- Count how many HSTs you will need, and divide that number by 2.
- Example: You need 24 HSTs. 24 ÷ 2 = 12.
- You will need to draw 12 grid squares.
- Draw the grid on the ¼" graph paper, using the calculations you made.
- In each grid square, draw a single diagonal line.
- Draw these diagonals so that they all connect together. If you look at a 2 × 2 grid of squares, this should look just like the lines drawn on the large square for 8-at-a-time HSTs.
- Draw the seam lines ¼" on either side of the diagonal lines. I suggest that you draw these seam lines in a different color to avoid confusion when you start to sew.
Cut one piece each of two different fabrics which are slightly larger than the size of the grid.

Sewing Instructions:
- Stack the two pieces of fabric on top of each other, right sides together.
- Place the grid paper one top of the fabric stack, making sure that all the grid lines are inside the edges of the fabric stack.
- Pin or baste the stack of grid paper and fabric to keep them from slipping. When I am making a large number of HSTs this way, I prefer to hand baste one long basting stitch in each triangle with a long, continuous thread. This method has many advantages over pins:
- Your fabric stays flat, whereas with pins, it would not be flat.
- There is no risk of stabbing yourself with pins as you sew.
- There is no problem with sewing or cutting over the basting threads, so it holds everything much more stable.
- You don’t have to remove these basting threads until the final step of the process.
- Sew on the seam lines that you drew. Do NOT sew on or beside the vertical and horizontal lines. Follow the path of the seam lines:
- Start in one corner and sew diagonally across the grid, then turn the stack 90° and sew diagonally again until you get to another edge of the grid.
- Sew in this manner until you get to another corner, then turn the stack 180° and sew on the other side of that set of diagonals.
- If there is still a set of diagonals which don’t have seams on either side of them, go to a starting corner of that set of diagonals and sew them in the same manner.
- Cut the HSTs apart by first cutting on the vertical and horizontal lines, including the outer edges of the grid, then cut on the diagonal lines.
- Carefully remove the paper and basting threads from the HSTs.
- Open the HSTs, press the seam allowances to one side, then trim the dog-ears.
- If your ultimate goal is to make QSTs, now go to Step 2 of the Quarter-Square Triangle Tutorial.