Use whichever method fits the piece. Square inches = width × height.
- Whole piece. For a single color, measure the finished piece: a 10″ × 12″ panel is 120 sq in. For round or odd shapes, measure the rectangle the shape fits inside.
- By color from the pattern. Use one glass line per color. Draw a rectangle around each piece of that color on the pattern, multiply width × height, and add them up. Three pieces of about 2″×3″, 2″×2″, and 1″×4″ = 6 + 4 + 4 = 14 sq in.
- Grid count. Lay 1″ graph paper or a clear grid ruler over the pattern and count the squares each color covers, counting partial squares as halves.
- By weight (most accurate). Set the amount-used unit to oz or g, then weigh a test piece of the same glass you can measure easily, like a 4″ × 4″ scrap (16 sq in). Weigh your cut pieces and the calculator converts weight to area.
If you weigh the whole sheet before and after cutting, scraps are already included, so set the waste allowance to 0%.