Patchwork Quilting: Master the Half-Square Triangle

Anyone wondering how to make a patchwork quilt with their scrap stash or using some of the fun, new commercial fabrics should learn the half-square triangle technique. It's one of the basic piecing techniques for patchwork quilting. Once you know how to do it, you can apply it to a lot of different patchwork projects, big and small.

Simple half-square triangle units let the fabric colors and patterns become the focal point in the design, like in this Half Square Quilt by Jeni Baker, featured in Modern Patchwork Winter 2015.

half square patchwork quilt jeni baker

Half Square patchwork quilt by Jeni Baker,
featured in Modern Patchwork Winter 2015.

To make a half-square triangle unit:

1. Decide on the measurement of your finished squares in the piece you are making. Once you have that measurement, add 7/8". For example, if the finished square = 2½˝, the cut size of your fabric squares should be 3-3/8˝. (For the math challenged, you convert the 2½ to 2-4/8ths, add 7/8s, and that gives you 3-3/8ths.) Cut your squares to this larger measurement.

2. Choose two squares you want to piece together to make a half-square triangle unit. Draw a diagonal line from corner to corner on the wrong side of the lighter of the two squares. (figure 1) Place the squares right sides together.

3. Sew a ¼" seam on each side of the marked line. Cut the fabric apart on the marked line to create two half-square triangle units. They should now measure your finished size.

4. Open and press to the dark side.

patchwork quilting half square triangles
This illustration, from Modern Patchwork Winter 2015, shows how
to mark, sew, and cut your squares to make two half-square triangles
for  patchwork quilting.

Making half-square triangles takes time, but once you've created all your squares, you can save time by string piecing or chain piecing them.

Making Jeni's quilt is a great way to learn this technique or practice your half-square triangle skills.

Looking for more ways to put patchwork and quilting together? The Winter 2015 issue of Modern Patchwork has a variety of patchwork quilt patterns and how-tos for modern patchwork projects whatever your skill level.

P.S. Have you ever made half-square triangles? Do you have tips to share? Leave a comment below.

Other topics you may enjoy:


Patchwork Quilts, Quilting Daily Blog

6 thoughts on “Patchwork Quilting: Master the Half-Square Triangle

  1. There are many different ways to make this unit. It depends on how many I need to make and do the need to scrappy or a large number from the same fabris, this definitely a great way to use up scraps.

  2. A caution I learned when pressing HST’s. As you flip open the seam to press, don’t just push the iron across the seam toward the corner. But rather, press from one side to the other, and then straight down…as if you are making an L shape in movement. This will prevent the bias edge from stretching away from a ‘square’ alignment. This tip came from an online class. Very helpful!

  3. I learned a faster way, decide on the finished size square you want double it and add 1.75 or 1 3/4″. So for a finished 4″ square, you need to cut two squares that are 9.75 or 9 3/4″ and draw a diagonal line across from all four corners. Stitch 1/4″ each side of diagonal lines and then cut between the lines of stitching as well as centre vertically and horizontally. You end up with 8 half square triangles. This is good if you are making a bigger project and you could use layer cake squares and trim to size after cutting apart, or just use them the size they end up which will be just a fraction larger than 4″ finished.