Quarter Square Triangle Quilt Tutorial

A quarter square triangle quilt tutorial – making a Quarter Square Triangle (QST) Quilt and writing an accompanying tutorial has been on my quilty to do list for several years now.

While I’ve done some quilting with QSTs, like this Quiltville Mystery Quilt, I’ve never made a quilt entirely from quarter square triangles and I decided to take advantage of this pretty, Christmasy layer cake to make giant blocks for my Quarter Square Triangle Quilt Tutorial.

How to Make Quarter Square Triangles

To make QSTs, start placing two squares of fabric right sides together.

What size are the squares Darcy, what size are the squares?

Well!  I’m glad you asked.  But you won’t be, because the answer is “math” and math is the worst part of quilting.

I’m just teasing.

You can make your quarter square triangles using squares of any size you like.  As long as all of your squares are the same size, you don’t actually need to know what size they are, and can avoid the math entirely.

But, if you aren’t afraid of a little bit of math, you can also plan the cut size for your squares in order have your blocks finish at the desired size.

Whatever your finished block size, add 1½” to the cut size.

That’s it.  All the math is behind us.  Let the quilting commence!

My squares are from a layer cake, so they are 10” to start.  The math above tells us my blocks will finish at 8½” once the quilt is complete.

After matching a pair of squares, draw a line from corner to corner of the lighter square.

Because my squares are so large, I chose to pin in several places (green lines), but the pins are just for comfort, they are not required, and wouldn’t be necessary if working with smaller squares.

Sew ¼” to the right of the line, then turn the squares and sew ¼” to other side of the line.  Cut the squares apart directly on the line.

Press towards the darker fabric, and you’ve got two half square triangles.  At this point, mine measured approximately 9½”.

Continue making half square triangles.  I used all 42 of the squares in the layer cake and ended up with a throw size blanket.  Make more or less as needed for a larger or smaller quilt using squares of any size.

Quarter Square Triangle Quilt Tutorial

To turn a half square triangle into a quarter square triangle, pick two half square triangles to match up.

Put the two half square triangles right sides together. 

To get a perfect seam intersection in the middle of the block, place these two squares together so that the seams nestle tightly together.  Do you see, on this zoomed in version of the last photo, how the dog ears don’t line up?  That’s because the two squares have the seams pressed in alternate directions which is what allows the seams to nestle together as tightly as needed.  Don’t worry, those dog ears will get trimmed off later.

Draw a line (shown in red) from one corner to the other and put several pins (shown in green) in place.  As before, sew ¼” from the line, on both sides of the line.

No photo of this next step, but like before, cut along the line and press towards the darker side of the quarter square triangle.  This makes two quarter square triangles that currently measure a little more than 9”.

The two QSTs are not identical but are reverse images of each other in terms of fabric placements.

I lied before.  There is a little more math involved in making these QSTs.  I’m sorry!

Trimming the Quarter Square Triangle Quilt Blocks

The last step in making quarter square triangles is to trim the blocks.  Again, you can follow my directions to make blocks the same size I did, or you can use some simple math to trim them to whatever size you want.

Remember your finished block size?  The number that helped you to know what size to cut your squares back at the beginning?

Take that number and add ½” to it. 

This is the size you want to trim your blocks to now.

For my quilt blocks, I started with 10” squares, so my blocks will finish at 8½” and I therefore want to trim them to 9”.

The best ruler for this trimming step is going to be on that has a 45-degree line on it, emphasized here in black.

Whatever number you ended up with when you added ½” to your finished block size, divide that number by 2. 

Yuck.  Math.

I’m sorry.

Whatever that number is, you want the center point of your block to be that distance from the edges where you will trim, and you want the 45-degree line to sync with the diagonal seam.  This is how you end up with the center point of the QST block in the exact center of the block.

For my blocks, trimming to 9”, I need that center point to be 4½” from each side so that it continues to be the center point (highlighted with a yellow circle).

Trim, trim, trim.  And that’s a Quarter Square Triangle quilt block!

Making a Quarter Square Triangle Quilt

Sew blocks into rows and rows into the quilt top.  My 42 QST blocks are set in 7 rows of 6 blocks each and my quilt finishes at 51½” by 59” which is just right for a couch quilt for the holidays.

Scout stopped by for a quick inspection but was too quick to snap a non-blurry photo.

I used fat quarters of three of the fabrics from the collection to make a scrappy-ish quilt binding.  The three fabrics are all the same print, but with red, white and green backgrounds.

Check back soon for a scrappy binding tutorial, including how I sew both sides of the binding on my sewing machine.  No more hand binding for me!

This quilt, along with others, is available for purchase in my Etsy Shop!