How much glass do I need? A per-color calculator

Every download on this site includes a glass list broken down by color, in square inches, already computed for your chosen panel size. This page explains the formula behind that list and lets you run it for any panel size and shape.

The formula

Glass needed per color equals that color's share of the panel area, multiplied by the panel's total area, multiplied by 1.15 to cover the 15 percent waste allowance for cutting errors, offcuts, and breakage. The 15 percent figure is a fixed planning allowance used consistently across every pattern on this site, not a measurement of any specific cutter's actual waste.

Why this is an estimate, not a cut list

This calculator assumes a square panel and a flat percentage share; it is a planning tool for buying enough sheet glass. The exact glass list shipped with each pattern download is computed from the pattern's real piece geometry at your exact size, not from this simplification, so use the shipped list when you are ready to cut.

See how to size a pattern for the width side of this question.