Half-Square vs. Quarter-Square Triangles

Half-Square Triangles

A half-square triangle, which is commonly abbreviated HST in most quilt patterns, is a triangle that was cut from a square. Traditionally one will start with a square of fabric the size specified in the pattern, and then cut it in half diagonally once to get two half-square triangles. HSTs can also be made in other ways, including making half-square triangles with jelly rolls. HSTs can be used in several different ways. One way they are commonly used is in units that make up a block, which is taught in this tutorial on half-square triangle piecing.

Another way half-square triangles are used is in a quilt design that is set on point. Because an HST is made from cutting a square in half, two sides of the triangle will have straight of grain sides and one will have a bias edge. The HST can be used in the corners of an on-point design to ensure that the outer edges of an on-point quilt will have straight of grain edges.

Quarter-Square Triangles

Quarter-square triangles, which are common abbreviated QST in most quilt patterns, are triangles that were again cut from a starting square. You will begin with a square of fabric the size specified in the pattern and then cut it in half diagonally twice to get four quarter-square triangles. QSTs are commonly used in units that make up blocks and also in on-point quilt layouts as well. Because of the way they are cut, they have two bias edges and one straight edge. Using a QST as a setting triangle on an on-point layout will again ensure that all of the outer edges of the quilt will be straight of grain edges.