How to Sew a Quarter Square Triangle Quilt Block – Kitchen Sink Quiltalong!

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Learn to sew the classic Quarter Square Triangle block! The QST (quarter square triangle) unit is found in many patchwork quilts. Sometimes quarter square triangle units are used in other quilt blocks, and sometimes the quarter square triangle is the quilt block!

Every quilter has to know this easy shortcut QST technique!

This free quilt block pattern shares how to sew a big beautiful QST block that finishes at 12”.

For more inspiration, check out the mini quilt that I designed using all quarter square triangles that I made from my scrap pile. I named this mini quilt Lunar Landing.

You could easily make a throw sized version of this mini quilt using the tutorial for a 12” QST block below!

I also used little QST’s to make some quilt magnets.

These easy instructions will show you how to easily sew two 12” QST blocks at a time.

There are 8 of these blocks in our Kitchen Sink Quiltalong Quilt, so the cutting instructions are for 8 blocks. Of course, you can easily adapt the technique and sew from 2 to 200 blocks!

Download the QST block pattern as a free printable PDF file.

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Instructions for sewing 12” (finished size) Quarter Square Triangle Quilt Blocks

These instructions make 8 QST blocks. Finished block size: 12’’ x 12’’ (they are 12 1/2’’ x 12 1/2’’ before you sew them in the quilt).

You will need:

  • 2-4 different colors or prints of fabric (this particular block uses 3 different colors: light gray, coral, and deep coral)
  • a rotary cutter acrylic ruler, and mat
  • sewing machine
  • thread (I suggest thread matching the light gray fabric)
  • ironing board and iron


  • Light Gray (or other light fabric):
    • cut 4 squares 13 1/2” x 13 1/2”
  • Coral (or other medium value fabric):
    • cut 2 squares 13 1/2” x 13 1/2”
  • Deep Coral (or darker value fabric):
    • cut 2 squares 13 1/2” x 13 1/2”


If you are not making our quiltalong quilt, here are some ideas:

  • Two squares of fabric will yield two QST blocks
  • If you would like different size QST units, start with squares of fabric 1 1/2” larger than your final size. Trim and square the QST units to be 1/2” larger than your final size, then sew them in your quilt block or quilt!


Use a scant 1/4’’ seam allowance and a medium stitch length such as 2-2.5.

1. Place one light gray square and one coral or deep coral square right sides together. Use a pencil or fabric pen to draw a diagonal line across the light gray square. This is a cutting line and should be drawn on the wrong side of the fabric if you are not using solids.

Pin the squares together.

2. Sew a scant 1/4’’ away from the cutting line on on both sides of the drawn line.

3. Cut the piece in half diagonally along the line. 

4. Open and press the two half square triangle (HST) units. Press the seams toward the darker (coral or deep coral) fabric.

Repeat with the remaining fabric squares to make 8 HST units, 4 that are light gray/coral and 4 that are light gray/dark coral.

5. Place one light gray/coral HST and one light gray/dark coral HST  right sides together with the seams aligned (nesting) and the light gray fabrics on opposite sides. Draw a diagonal line that crosses over the seam on the top HST. This is a cutting line. Pin the HST units together.

6. Sew 1/4’’ away from the cutting line on on both sides of the line.

7. Cut the piece in half diagonally along the line.

8. Open and press the quarter square triangle (QST) blocks. Trim each block to 12 1/2’’ square. 

Tip: I have used my 12 1/2” square ruler to square up every block in this quiltalong quilt so far and I love it!

Repeat with the remaining HST units to make 8 QST blocks that are all the same.

This is Block #4 in our Kitchen Sink Quiltalong

Get ready to sew all your favorite quilt blocks this year! This is the year that we are going to sew everything but the kitchen sink in our Kitchen Sink 2022 Quiltalong.

This bold graphic quilt is perfect for learning new quilt making skills that build on one another, or for putting skills you already have into a big beautiful quilt.

Tips: As you work block by block on your kitchen sink quilt, save your scraps because you will be able to use them later on.

These awesome scrapbooking bins are perfect for keeping your finished blocks safe until it’s time to sew them together into a quilt top.

Here are the 10 free quilt block patterns in the Kitchen Sink Quiltalong:

Don’t miss all my other free quilt patterns, too!


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