have been making a lot of quarter square triangles lately for a variety
of different projects, so I thought it might be good to share my
favorite method for making these versatile blocks.
With this method there isn’t any reason to create the quarter square triangle
block using triangles–by using square pieces of fabric you eliminate much of the trouble created by using working with the bias edges of triangles. And, what’s even better is that this method can be adapted to any pattern.
Step 1: Figure out the size squares you need. To make 4 quarter square triangle blocks, start out with four squares of fabric that each measure 1″ larger than the unfinished size of your desired block. So for a 4″ unfinished block (3 ½″ finished) you’ll need squares 5″ x 5″.
For this tutorial I’m using 4 different fabrics and creating quarter square triangle blocks that contain each of these four fabrics; however, this method works just as well for two-color or three color quarter square triangle blocks.
Step 2: Begin by placing two squares right sides together. Next you will draw a line diagonally across the back of the lighter block. Sew ¼″ on either side of your line. In the photo above, my diagonal line doesn’t show, but I went over the stitching lines with a pen so they’d show up better.
Step 3: After you have sewn both seams ¼″ away from the center, cut in half diagonally on the center drawn line.
Step 4: Each pair of squares will give you a pair of completed half square triangles. Press toward the darker fabric. Make sure you press carefully and be sure to press again on the front side to make sure that all of the seam is pressed neatly with no puckers or bubbles. We’re half-way there!
Step 5: Now, place two half-square triangles together again, right sides together. “Nest” the seam allowances. To nest seam allowances, butt the seams right next to each other. The seams should smoothly nest together with no gaps in between. It’s important not to have any gaps in between the seams so that everything will match correctly in the center of your block. Draw diagonal lines down the center and again sew ¼″ on either side just as you did in step 2 above.
Step 6: Again cut the blocks in half on the diagonal. Each pair will give you 4 quarter square triangle units.
You now have 4 beautiful quarter square triangle blocks, but there is one more step to finish up.
Step 7: Next, use a ruler with a diagonal line to trim your block to the exact size. Any square ruler the same size or larger than your block will work; however, I prefer the “Fit to be Quarter” ruler by Monique Dillard. I’ve used a variety of other rulers, and the reason I like this particular ruler the best is because there are additional markings which allow you to easily trim the blocks to any size up to 6 ½″ x 6 ½″ in increments of ¼ inches–with no guessing. Most other rulers only give you the option to trim every half inch. Also, Monique also makes a larger size ruler which will trim quarter square triangle units up to 9 ½″.
To make trimming easy, line up the diagonal line on the ruler with the diagonal seam of your block. Make sure the mid point line is in the correct place. You will notice that this block will be 4″ x 4″ unfinished, so the 2″ line goes right through the middle of the block where the four diagonal seams intersect.
Trim the right side and top, then flip your block and trim the other two sides. Always make sure the diagonal lines on the ruler match up with the diagonal seams on your block.
Now you’re finished! You’ve created four beautiful quarter square triangles with minimal bias to worry about!
Edited: You can also watch my video tutorial above which illustrates more clearly all of these steps!
Thanks so much for stopping by!