How to Square Up Half-Square Triangles

Half-square triangles are fun blocks to add to nearly any design. Because half-square triangles, also referred to as HSTs, are squares made from two triangles that have a bias edge, they can become distorted when stitched and pressed. To help keep this from happening, HSTs are generally made oversized and then trimmed down to the correct measurement, also known as squared up. Ashley Hough shows how you can save time when making half-square triangles by squaring them up as triangles before pressing them into squares.

Squaring Up

When making oversized half-square triangles, it is common to stitch them together, press them into a square, and then square them up using a square ruler. This is generally done by trimming two sides at one time, rotating the block, and then trimming the other two sides.

While this is efficient, it is essentially an extra step because you have to trim it twice. Ashley shows how to skip a step by only trimming once. She does this by trimming while the triangles are still together before they are pressed into a square. She shows how to do this with a standard square ruler, explaining where to line up the stitching line of the half-square triangle on the ruler.

She also shows how to do this using a ruler specifically designed for this technique. Once you have mastered both methods of squaring up half-square triangles, learn more about using them in your design with half-square triangle piecing. After you learn about different ways of squaring up half square triangles—check out additional tutorials on different ways to make them. While they are generally made from triangles or squares, another fun method is to make them from strips. See how to make half-square triangles with jelly rolls.