Stained Glass Lead Came Length Calculator
Work out lead came or copper foil length for a stained glass panel from its size and piece count.
Returns metres, feet, and how many strips or rolls to buy.
Calculating lead came for stained glass panels
Lead came (pronounced “kaim”) is the H-shaped channel that holds glass pieces together in traditional stained glass. Copper foil (the Tiffany method) is an alternative where thin copper tape wraps each piece’s edge. Both methods require estimating the total linear length of material.
Lead came estimation formula
Add up the perimeters of all the pieces and you have counted every interior line twice, once from each side, and every border edge once. So take the border off before halving, not after:
Interior came = (Total of all piece perimeters − Panel perimeter) ÷ 2
Border came = Panel perimeter
Total came = Interior + Border, plus 15% waste
That correction matters more than it looks. Halving the whole perimeter total and then adding the border on top counts the border one and a half times. On a big panel cut into many small pieces that is under 10% too much came. On a small panel with a few large pieces, where the border is most of the metal in the thing, it is over 30%.
How long is an average perimeter, really?
People underestimate this badly. For n roughly equal pieces filling a panel of area A, the average perimeter is about 4 × √(A ÷ n). Thirty pieces in a 60 × 90 cm panel means each one covers 180 cm², which is a square 13.4 cm on a side, so its perimeter is nearly 54 cm. Not 30.
| Pieces per m² | Average piece perimeter | Description |
|---|---|---|
| 15 to 25 | 80 to 100 cm | Large rectangles, few curves |
| 25 to 40 | 63 to 80 cm | Mixed shapes, some curves |
| 40 to 60 | 52 to 63 cm | Smaller pieces, intricate design |
| 60 to 100 | 40 to 52 cm | Very small pieces, complex curves |
Leave the perimeter box empty and the calculator works it out from the panel and the piece count. Fill it in if you have measured, and it will tell you when your figure and the panel disagree.
Lead came sizes. Came is sold by the width of the visible face, and the heart is the thin web down the middle that the two channels sit either side of. Those are different numbers, and the heart is always the smaller one: usually 1.6 mm (1/16 inch) on ordinary H-came, up to about 3 mm on heavy structural profiles.
| Face width | Typical heart | Best for |
|---|---|---|
| 3/16" (4.8 mm) | 1.6 mm | Fine detail, small pieces |
| 1/4" (6.4 mm) | 1.6 mm | Standard interior lines |
| 5/16" (8 mm) | 1.6 to 2 mm | Heavier interior and emphasis lines |
| 3/8" (9.5 mm) | 2 mm | Borders and structural runs |
| 1/2" (12.7 mm) | 2 to 3 mm | Large panel borders, window perimeters |
Cut each glass piece back by half the heart width from your pattern line on every edge. Skip that and the finished panel comes out bigger than the opening you made it for.
Worked example: a 60 × 80 cm panel, 24 pieces
Average perimeter = 4 × √(4,800 ÷ 24) = 4 × 14.1 = 56.6 cm Total of all perimeters = 24 × 56.6 = 1,358 cm Border = 2 × (60 + 80) = 280 cm Interior = (1,358 − 280) ÷ 2 = 539 cm Total = 539 + 280 = 819 cm, and with 15% waste 9.4 m
Lead came comes in 6-foot (1.83 m) strips, so 9.4 ÷ 1.83 = 5.1, meaning 6 strips.
Copper foil alternative
With the Tiffany method every piece is wrapped individually, so nothing is shared and you need tape for the full perimeter of every piece, plus a little overlap where the ends meet.
Copper foil = Pieces × (Average perimeter + 1 cm overlap) × 1.05 for waste
Same panel: 24 × (56.6 + 0.95) × 1.05 = 1,450 cm, or 14.5 m.
Foil is normally sold in 36-yard rolls, which is 108 feet or about 33 m, so one roll covers this panel with plenty spare. Widths run 3/16", 7/32" and 1/4", matched to the glass thickness rather than to the panel; the copper foil calculator works that pairing out.
Zinc came for borders. Plenty of makers use zinc U-channel around the outside instead of lead, because it is far stiffer and stops a large panel bowing. The border length is worked out the same way; only the material changes.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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