Two at a Time Half-Square Triangles
The two-at-a-time method is a reliable way to make half-square triangles quickly and accurately. Below you’ll find the basic construction steps and cutting reference for common HST sizes.
Construction Steps
Place two squares right sides together.
On the back of one square, draw a diagonal line from corner to corner.Sew a scant ¼" seam on both sides of the marked line.
Accuracy here matters. A true scant seam ensures the HSTs finish at the correct size.Cut along the drawn diagonal line.
This separates the unit into two half-square triangles.Press and finish.
Open the HSTs and press seams according to the pattern instructions. If no pressing direction is specified, press toward the darker fabric to avoid shadowing.
Trim dog ears and check size. Seam accuracy is key. A true scant ¼" ensures correct HST size. These HSTs should not require trimming if the seam allowance is accurate.
Half-Square Triangle Cutting Sizes
This table shows the cutting sizes needed to make two half-square triangles at a time, from 1 ½″ to 7″ finished.
Cutting math: Starting square size = finished HST size + 7/8"