Quarter Square Triangles - Easiest Methods (QST)

These nifty quilting blocks have a confusing name! Quarter square triangles are actually squares. Each square unit is made up of four 90 degree triangles. They are useful building blocks for numerous quilt designs and are known as QST’s in quilting terms.

What are Quarter Square Triangles Used For?

Quarter square triangles may be used by themselves as part of more intricate quilting designs such as the Ohio Star quilt block.

Types of Quarter Square Triangles

There are variations on how to make quarter square triangles, and on how the finished block will look. The completed blocks may look like any of these, all with a similar method of construction.

Hourglass QST’s - Has the same fabric top and bottom so it looks like an hourglass.
Bow-tie QST’s - Made the same as the hourglass type, but turned on its side.
Multi-colored QST’s - Made with four different fabrics
Split Quarter QST’s - Made with three fabrics. (Once again, a rather misleading name!)

Quilting Quarter Square Triangles - Supplies

Fabric- closely woven cotton fabric is best. Use fat quarters of quilting fabric for a great choice of patterns.
Strong thread
Pen - Removable marking pen
Cutting Tools - Rotary cutter, self-healing cutting board, quilting ruler
Basics - Sewing machine, iron and ironing board
Useful, but not essential - a square quilting ruler and spray starch.

How to Make Quarter Square Triangles

Here I will show you several methods and variations of making quarter square triangles

Method 1 - Using 4 triangles
Method 2 - Using half square triangles

Method 2 is generally best for more consistent results. This is the one I usually use.

Method One - QST Using 4 Triangles

This is the simplest method, but can result in slightly wonky squares! You simply cut out four equal-sized 90-degree triangles, and sew them together to form a square.

If you are using this method, be sure to cut your triangles with the straight grain on the outer edge of the triangle to prevent stretching.

Sew two small triangles together to make a larger triangle, then sew the two large triangles together.

PROS - This method can be useful if you want specific colors in a specific order to make up your larger quilt pattern. It takes the calculations out of working out symmetry and mirror images!
CONS - It is more time-consuming, and you may have some issues with sewing the bias edges together. To overcome this, a little spray starch on your fabric will help prevent any stretching. Simply spray, then cut.

Method Two - QST Using Half Square Triangles

Create 2 Half Square Triangles

Familiarize yourself with the methods of making the half square triangles before you attempt this method! You will need to sew 2 half square triangles.

There are several methods you can use to make half square triangles but I find this one the easiest.

Cut 2 squares of equal size
Put them right sides together.
Draw a diagonal line.
Stitch ¼ inch on either side of the marked line. Use small stitches of 1.5.
Cut along your marked diagonal line with a rotary cutter.
Press open your half square triangles. The seam should be pressed towards the darker color so it does not show on the outside.

Hourglass Quarter Square Triangles

Create your 2 half square triangles (HST’s) as previously described. Remember to press your seams to the darker side before you continue with the next step.
Place your HST’s right sides together, nesting the seams. Your seams should be laying in opposite directions. i.e. one facing up, one facing down. Your different colors must also be opposite- darker fabric on top of the lighter fabric, and vice versa.
Draw a diagonal line from corner to corner. It must be at 90 degrees to your seam, and it will bisect the seam.
Sew a seam ¼” (6mm) on either side of your line.
Cut along the line in between the seams.
Press well each time you finish a seam, this will keep each seam flat before adding the next seam. Also, remember to just press, not slide your iron along the fabric. Especially with these bias seams!
Trim to size. More about trimming quarter square triangles to size later!

Bow-tie Squares

Are made in exactly the same way, but rotated 90 degrees.

Multi Colored Quarter Square Triangles

These can also be called scrapped quarter square triangles.

To make these squares, you use the same method as above, but the HST’s must be made in different colors. You will use four different colors.

Your final blocks will not turn out exactly the same with this method, they will be mirror images. You need to take this into consideration when planning your full quilt. If you are planning to make a scrappy quilt, this will not matter.

Split Quarter Square Triangles

To make these, you will still use the same quick piecing method, but now you must replace one of your HST’s with a solid square.

HST to Make Split Quarter Triangles — HST to Make Split Quarter Square Triangles

Place the solid square and the HST right sides together and draw a diagonal line. The line should go across the seam on the HST.
Stitch a ¼ inch (6mm) seam on each side of the line.
Cut along the line.
Open out and press.
Trim your quarter square triangle to size.

This will make two quarter square triangles, but again, they will be a mirror image, not identical. If your quilt has specific orientation requirements, save the blocks you have made which face the wrong way, keep all these as well as practice blocks in a large box somewhere, and you will eventually have enough units to put together a scrappy quilt! Quilters are generally hoarders!

Quarter Square Triangles Cheat Sheet - Starting Sizes Of Squares

Of course, before you even start constructing these quarter square triangles, you need to know what size to cut your original squares.

It can be useful to cut the starting squares larger than just adding a seam allowance, and then trim your final squares down to size. This allows some wiggle room for stretching while stitching, or for slightly uneven seams.

FORMULA: Starting square = finished QST size +1 ½” (4 cm)

So if you are aiming for a 6” (15cm) QST, you must start with 7 ½” (19cm) square.

Please note that cm conversions are rounded off, they are not precise! Do not ever combine inch and cm measurements, your blocks will not work out accurately! Choose which unit of measurement you want to work with beforehand.

Then when the quarter square triangles are assembled, trim off the dog ears and trim to the required size.

Quarter Square Triangle Chart

For those who hate doing the math, here is a chart for cutting quarter square triangles:

Finished QST Size	Cut Starting Squares To	Trim Assembled QST To	Center Point
2” (5cm)	3 ½” (9cm)	2 ½” (6.3cm)	1 ¼” (3.15cm)
2 ½”(6.3cm)	4”(10cm)	3”(7.6cm)	1 ½” (3.8cm)
3”(7.6cm)	4½”(11.3cm)	3 ½” (9cm)	1 ¾” (4.5cm)
3 ½”(9 cm)	5”(12.5cm)	4”(10cm)	2”(5cm)
4”(10cm)	5 ½ “(13.8cm)	4 ½” (11.3cm)	2 ¼” (5.65cm)
4 ½”(11.3cm)	6”(15cm)	5”(12.5cm)	2 ¾” (6.25cm)
5”(12.5 cm)	6 ½”(16.3cm)	5 ½” (13.8cm)	2 ¾” (6.9cm)
5 ½”(13.8cm)	7”(18cm)	6”(15cm)	3”(7.5cm)
6”(15cm)	7 ½”(19.3cm)	6 ½” (16.3cm)	3 ¼” (8.15cm)
6 ½”(16.3cm)	8”( 20cm)	7”(18cm)	3 ½” (9cm)
7”(18cm)	8 ½” (21.3cm)	7 ½” (19.3cm)	3 ¾” (9.65cm)
7 ½”(19.3cm)	9”(23cm)	8”(20cm)	4”(10cm)
8”(20cm)	9 ½” (24.6cm)	8 ½” (21.3cm)	4 ¼” (10.65cm)
8 ½”(21.3cm)	10”(25cm)	9”(23cm)	4 ½ “(11.5cm)
9”(23cm)	10 ½” (26.8cm)	9 ½” (24.6cm)	4 ¾” (12.3cm)
9 ½”(24.6cm)	11”(28cm)	10”(25cm)	5”(12.5cm)
10”(25 cm)	11 ½” (29.3cm)	10 ½” (26.8cm)	5 ¼” (13.4cm)
10 ½”(26.8cm)	12”(30cm)	11”(28cm)	5 ½” (14cm)
11”(28cm)	12 ½” (31.3cm)	11 ½” (29.3cm)	5 ¾” (14.65cm)
11.½”(29.3cm)	13”(33cm)	12”(30cm)	6”(15cm)
12” (30cm)	13 ½” (34.3cm)	12 ½” (31.3cm)	6 ¼” (15.65cm)

Quarter Square Triangles Cutting Chart

How to Trim Quarter Square Triangles

When trimming the quarter square triangles to size, it is useful to have a square quilting ruler.

For this step, you need to know what the unfinished size will be of your QST’s. So say you are aiming for a 6” (15cm) finished square. You must trim your constructed square to the UNFINISHED size, which will be 6 ½” (16.5 cm) to give yourself a seam allowance.

How to trim quarter square triangles:

Line up your ruler with your square block.
Line up the central point (i.e. where the seams cross over) with the central blocks on your ruler.
See chart above for center point measurements.
For the 6”(15cm) block this will be at the 3”(7.5cm) mark on the ruler.
This central point is important to get even blocks.
Your block may not be perfect, you may have to make tiny adjustments and jiggle things around a little bit. Just get it as neat and as central as possible!
Trim the right-hand side and the top along the edges of your ruler. Then rotate the block 180 degrees, line it up as before with the central point, trim the right side and the top again.
If you are left-handed, you will line the ruler up on the opposite side of the block, hold it still with your right hand and trim with your left hand.

Ideas for Using Quarter Square Triangles

These blocks have a number of applications, some of which are:

Hourglass Quilting
Ohio Star - You can see that this is made up of four QST’s and five full squares.
Card Trick - This one has only one full QST in the center, Four split QST’s, and four HST’s.

Quarter Square Triangles - In Conclusion

My personal opinion is that the most interesting quilts are the ones made combining QST’s, HST’s and full squares. Even if you don’t have a large quilt project lined up using quarter square triangles, enjoy the process of learning and challenging yourself! Save all those trial squares. Experiment and see what works best for you before you attempt a masterpiece quilt using quarter square triangles!