Half Square Triangle vs. Quarter Square Triangle

Triangles can make up large portions of many quilt designs, but not all triangles are the same, even though they might look like they are at first glance. Learn the difference between half square and quarter square triangles and when to use them.

Types of Quilting Triangles

Grain of Fabric

Kelly Ashton begins by talking about the grain of fabric, as this is the most important distinction between half square and quarter square triangles. She explains that there are two directions that are the straight of grain on fabric, which are parallel and perpendicular to the selvage of the fabric.

The Bias

On a forty-five degree angle between the two straight grain directions is what is known as the bias. The bias is the direction of the fabric that has the most stretch. Depending on how a triangle is cut, that bias edge ends up on either the two shorter sides of the triangle or the longer side of the triangle.

Half Square Triangle

Kelly then shows how to cut a half square triangle. This type of triangle starts with a square, which is then cut in half diagonally to make two triangles. The bias edge ends up on the longer side of the triangle.

Quarter Square Triangle

She then shows how to cut a quarter square triangle. This type of triangle starts with a square, which is then cut in half diagonally twice to make four triangles. The bias edges end up on the two shorter sides of the triangle.

Placement

Kelly then shows where these triangles should be placed when sewn together into blocks and units in order to ensure that the bias edges of a triangle do not end up along the outer edges of a block or unit.

Once you learn the difference between half square and quarter square triangles, play around with different ways to cut and make them, including how to make half square triangles with jelly rolls, and then turn those half square triangles into a quilt!