Half-Square Triangle (HST) Calculator

Calculate the starting square size needed for half-square triangles at any finished size.

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How It Works

Half-square triangles (HSTs) are one of the most versatile quilt units. For the standard 2-at-a-time method, cut your starting square at the finished size plus 7/8 inch. This accounts for two 1/4-inch seam allowances plus the diagonal seam. The 4-at-a-time and 8-at-a-time methods are more efficient for large quantities but require larger starting squares.