Stained Glass Copper Foil Calculator
Calculate copper foil tape length and rolls for Tiffany stained glass from piece count and average perimeter.
Returns total foil in feet and 36-yard roll count.
The copper foil (Tiffany) method of stained glass construction wraps each glass piece with adhesive-backed copper tape before soldering. Calculating foil usage prevents running out mid-project.
Core Formula: Total Foil Length = Sum of all piece perimeters + Overlap allowance
For each piece: Foil per piece = Perimeter of piece + Overlap (typically 0.25–0.5 inches per piece)
Estimating Perimeters by Shape: Since stained glass pieces are irregular, approximate each piece by its closest geometric shape:
| Shape | Perimeter Formula | Example (4" wide) |
|---|---|---|
| Square | 4 × side | 16 inches |
| Rectangle | 2 × (L + W) | varies |
| Triangle | a + b + c (≈ 3 × avg side) | ~12 inches |
| Circle | π × diameter | 12.6 inches |
| Irregular | measure or estimate | varies |
Average Perimeter by Piece Size: A common estimation method uses average piece size:
| Piece Category | Avg Perimeter | Description |
|---|---|---|
| Small (under 3") | 8–10 inches | Detail pieces, eyes, accents |
| Medium (3"–5") | 12–16 inches | Standard panel pieces |
| Large (5"–8") | 18–24 inches | Background, sky sections |
| Very large (8"+) | 26–36 inches | Borders, large fills |
Worked example, a 45-piece suncatcher panel:
- 10 small pieces: 10 × 9" = 90"
- 25 medium pieces: 25 × 14" = 350"
- 10 large pieces: 10 × 21" = 210"
- Subtotal: 650 inches
- Overlap (0.375" per piece × 45): 16.9"
- Waste (5%): 33.3"
- Total: 700 inches, just over 58 feet
Foil roll sizes: Standard rolls are 36 yards, which is 108 feet or 1,296 inches. Roll length is the same whatever width you buy, so a roll goes about as far on 3/8" foil as it does on 3/16". What changes the count is piece size: one roll covers roughly 85 medium pieces, or about 58 large ones.
Picking the width. The rule is simple once you see it. The foil has to wrap the edge of the glass and fold over onto both faces, so the width you need is the glass thickness plus about 1.3 mm on each side. That leaves you with:
| Foil width | Suits glass | Overhang per face |
|---|---|---|
| 3/16" (4.8 mm) | 2 mm thin or antique | 1.4 mm |
| 7/32" (5.6 mm) | 3 mm, the standard sheet | 1.3 mm |
| 1/4" (6.4 mm) | 4 mm, or 3 mm with fatter solder lines | 1.2 mm |
| 3/8" (9.5 mm) | 6 mm bevels and thick fused pieces | 1.8 mm |
Too narrow and the foil has nothing to grip, so it lifts at the corners while you solder. Too wide and you get a heavy black line around every piece, which is a design decision rather than a mistake, but make it on purpose. Enter your glass thickness below and the calculator will check the pairing.
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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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