How to Sew Half-Square Triangles (Method 6 of 6)

The half-square triangle is a basic piece used in many quilt blocks. Very simply, it is a square that is cut in half from corner to corner (diagonally) to create two triangles within one patch.

As amazing as it sounds, there are several ways to sew these units together. Some of these methods increase the accuracy of the resulting patch (for example Methods 2 and 4). Other methods increase the speed or convenience of sewing many half-square triangles (Methods 5 and 6).

Which method you use depends upon personal preference.

Difficulty: Moderately Easy

Instructions

Things You'll Need:

• Fabric
• Thread
• Needle or Sewing Machine
• Scissors or Rotary Cutter
• Ruler

1. 

   Using this method, you will cut large, but manageable rectangles, mark sewing and cutting lines, sew them, and then cut the triangles. The preparation/marking time is less than if you were marking each square separately. The sewing time also is less since there is only one unit of fabric to handle instead of individual triangles.
   
   Determine how large to cut the rectangle pieces of fabric. To determine the cut size, take the finished size and add ⅞” to both sides. For example, if you are using 2” squares (finished size), the cut size will be 2⅞” square.
   
   Figure out how many of these squares you would like to have on your fabric. Using the above example, 6 squares across would require a 17¼” length, and 4 squares down would require a 11¼” width of fabric. This configuration would result in 24 squares of half-square triangles. You may wish to add extra on each of the sides.

2. 

   Using this method, you will cut large, but manageable rectangles, mark sewing and cutting lines, sew them, and then cut the triangles. The preparation/marking time is less than if you were marking each square separately. The sewing time also is less since there is only one unit of fabric to handle instead of individual triangles.
   
   Determine how large to cut the rectangle pieces of fabric. To determine the cut size, take the finished size and add ⅞” to both sides. For example, if you are using 2” squares (finished size), the cut size will be 2⅞” square.
   
   Figure out how many of these squares you would like to have on your fabric. Using the above example, 6 squares across would require a 17¼” length, and 4 squares down would require a 11¼” width of fabric. This configuration would result in 24 squares of half-square triangles. You may wish to add extra on each of the sides.

3. 

   On the wrong side of the lighter fabric, draw the cutting lines of your squares. Using the same example, mark 24 squares that measure 2⅞ ” each. Then draw a diagonal line through the center of each square. This, too, is a cutting line.

4. Place the fabric right sides together (one marked and the other one not marked). Sew each of the squares two times, ¼” on each side of the diagonal line through the center of the square.

5. 

   Press the sewn rectangle to set the stitching. Cut on the drawn lines to make your triangles.
   
   First, cut the lines to make strips.

6. 

   Once you have strips, cut them apart into squares.

7. 

   And, finally, cut the squares apart, making triangles.

8. 

   Open each half-square triangle, and press (preferable press the seam allowance so it is under the darker fabric).

9. 

   Trim the “dog ears” off of the edges of the squares.

Resources

• How To Quilt
• Quilt Block Library