Quarter-Square Triangles Calculator

Getting clean QSTs every time

Press the first HST seam open before making the second diagonal cut. This reduces bulk at the center where four seams converge — pressing to the side here just creates a lump that throws off your next seam. If you're seeing puckers at the center of your finished QSTs, this is almost always why.

The grain line advantage is the whole reason QSTs exist. All four outer edges end up on straight grain, which means your blocks won't stretch and wave the way HSTs can. This matters most at the quilt's perimeter and anywhere blocks meet sashing.

Starch before cutting — heavy starch, not a light spritz. The interior bias edges in a QST are handled more than in an HST (two sewing steps instead of one), so the fabric needs to be stiff enough to resist stretching through all that handling. Cut a little generous and trim to exact size with a square ruler after pressing.