Many quilts are made up of a variety of half square triangles (two triangles cut from one square). The half square triangle is a common unit in pieced quilt block patterns. It is two right angle triangles joined together to make a square. Whenever possible, with pieced units and blocks, it is best to position the straight grain of the fabric along the outside edge. There are several methods of cutting and constructing these units. We will discuss two of them.

When working with these units, you must first know the desired finished size when sewn into the quilt block. To do this, you must add the seam allowance to determine the cut size of the shapes.

A drafted pattern of this shape is helpful in understanding this concept, especially when working with triangles. First draw the finished size of the quilt square on the graph paper. Draw a line diagonally from corner to corner to show the finished triangle size. Now mark lines around a single triangle with the amount of your seam allowance. For our example we will add a half inch. This is the final cut size of your triangle. The width equals the final cut size of any squares you cut before you cut triangles.

Right square triangles can be quickly and accurately cut with a rotary cutter. Learn these two common methods.

**One Method For Cutting Quilt Triangles**

First cut squares in the size specified in your directions. Then line up a ruler’s edge with opposite corners of a square. Cut along the ruler’s edge to cut the square in half diagonally; separate the triangles. Repeat with the remaining squares. Because the triangles’ long edges are on the bias, avoid stretching them when piecing so you don’t get distorted seams.

**Another Method For Cutting Quilting Triangles**

First cut squares in the size specified. Then line up a ruler’s edge with opposite corners of a square. Cut along the ruler’s edge to cut the square in half diagonally, but do not separate the two triangles created. Instead, line up the ruler’s edge with the remaining corners and cut along the ruler’s edge to make four triangles total; separate the triangles. Because the triangles’ short edges are on the bias, avoid stretching them while piecing so you don’t get distorted seams.