A WORKBENCH GUIDE · UPDATED OCTOBER 9, 2026

Estimate stained glass materials before you buy.

Separate the glass area, piece edges, joins and solder. Each answers a different question.

1. Glass area: include coverage and cutting waste

For a rectangular panel, net glass area = width × height × coverage. Multiply that by (1 + waste percentage / 100) to get a planning purchase area. Convert square inches to square feet by dividing by 144.

Example: a 12 × 18 inch panel at 92% coverage with 15% cutting waste gives 228.528 square inches, or about 1.587 square feet. This does not tell you whether particular pieces fit a sheet: color allocation, grain and layout can require more glass.

2. Copper foil: count each piece edge

Foil wraps the perimeter of each separate piece. An internal join has an edge on each neighboring piece, so both need foil. For a filled rectangular panel: foil length = (2 × measured internal join length + outside border) × (1 + allowance / 100).

A 10 × 10 inch panel split into two 5 × 10 inch pieces has a 10 inch internal join and a 40 inch outside border. The two piece perimeters total 60 inches of foil before overlap and allowance. With 10% allowance, plan 66 inches.

3. Lead came: count each join once

Came between two adjacent pieces is one shared length. The same two-piece panel needs 10 inches of internal came plus a 40 inch border, or 50 inches before allowance. Actual border profiles, miters and stock lengths still matter. Divide the allowance-adjusted length by the roll or stick length and round the package count up.

Measured joins or piece averages?

Measured joins are preferable for complex patterns. If only average piece perimeter is known, the app estimates internal joins as (piece count × average perimeter − outside border) / 2. This assumes a filled rectangular panel without holes. A perimeter sum shorter than the outside border is inconsistent and should be corrected.

4. Solder: use a rate from your own work

Solder weight depends on your seam length, whether you solder both sides, your grams-per-length rate and waste. The app uses those inputs and rounds spool count up. Foil length and solder seam length are different; do not use the doubled internal foil length as the solder path.

For example, 20 inches of seam at 10 grams per 10 inches, both sides and 25% waste uses an estimated 50 grams. One 100 gram spool covers that planning amount.

What these estimates leave out

Pattern layout, complex borders, holes, rework, overlaps and bead size can change actual use. Check your supplier's stock dimensions and record consumption from finished projects to refine rates.

For the construction method, see Delphi Glass's guide to wrapping individual glass edges with copper foil.

Next: include materials and labor in a stained glass project price.