How to make the Perfect Half Square Triangles

Half Square Triangles or HSTs are one of the most common quilting block units.

Watch this video or read on to learn how to make half square triangles.

STEP 1:
To make half square triangles, first you must determine the size squares you need to cut.

In order to get the correct finished square size, most people will cut the fabric squares 7/8 inches larger then the finished square size they want. For instant, if you want a finished square size of 3 inches, you would cut fabrics squares 3 7/8 inches.

However, I like to cut the fabric squares a little larger because the half square triangles units may distort when sewing them the units together. By the unit being larger, I can trim the unit to the correct size. I prefer to cut the squares 1 inch larger than the finished square size. So if I want a finished square size of 3", I cut the fabric square 4 inches.

After determining the fabric square size, cut two squares of contrasting colors. Usually you use a light and a dark fabric.

STEP 2:
On the wrong side of the lighter fabric, with a pencil, draw a diagonal line from corner to corner.

STEP 3:
Place one light square and one dark square with right sides together, aligning all four sides. Pin in place.

STEP 4:
Sew 1/4" away from the marked line on each side. If you have a 1/4" quilter presser foot, this is very easy to do. If you do not have a 1/4" presser foot, you will need to draw the sewing lines on the fabric.

STEP 5:
Cut the unit in half along the center line.

STEP 6:
Before opening the unit, place the triangle square up ruler on the triangle unit and match up the marking for the finished block size along the seam. Trim as needed.

We have also discovered this Trim-Lock Quilt Block Trimming Tool that makes trimming half-square triangle blocks quick and easy!  This tool is used after you've pressed the block open.  Click the link to view the demonstration for this Trim-Lock tool.

STEP 7:
Press the seam to set the seam. Then open the block, right side up. With the tip of the iron, carefully press along the seam making sure the seam allowance in the back is pressed toward the darker color.

STEP 8:
Cut off the dog ears. Dog ears are tiny pieces of fabric that stick out at the corners.

STEP 9:
Check the measurement again. The unit should measure 1/2 inch wider and taller then the desired finished unit size.

 A Half Square Triangle

Get a Triangle Square Up Ruler and other quilting supplies from the following affiliate links.