Pinwheel Block Calculator 🌀

How to Use the Pinwheel Block Calculator

Enter your finished block size and how many pinwheel blocks you need. The calculator uses the 2-at-a-time HST method, which produces 2 HST units from each pair of squares sewn together.

Cut equal numbers of squares from Fabric A (light) and Fabric B (dark). Layer one A and one B square right sides together, draw a diagonal line, sew 1/4" on each side, cut apart, press, and trim to the exact HST size.

Arrange 4 HSTs with the light triangles rotating around the center to form the pinwheel. Press all seams toward the darker fabric and nest the center seams for a flat, accurate intersection.