Stained Glass Solder Weight Calculator

Estimating solder consumption for stained glass projects is essential for budgeting and purchasing. The amount of solder needed depends on the total seam length, the soldering technique (copper foil vs lead came), the width of the foil or came, and whether you create flat seams or raised beads.

Solder Consumption Formula

Solder weight (g) = Seam length (cm) × Consumption rate (g/cm) × 1.6

The 1.6 is the two faces: a full bead on the front, then about 60% of that again on the back, where you are filling the channel rather than shaping a rounded top.

Consumption Rates by Technique

Those rates are for one face. A solder bead is a rounded cap, not a rectangular ridge, so its cross-section is roughly two thirds of width × height. In 60/40 solder at 8.5 g/cm³ that works out to width × height × 8.5 ÷ 150 grams per centimetre, which is where the three numbers above come from. Change alloy and the weight moves with the density.

Lead came is counted differently. Solder never runs along a came line, only at the joints where lines cross, so the answer depends on how many joints there are rather than how long the seams are. A grid of n pieces has roughly n + (W + H) × √(n ÷ area) − 3 joints, each taking about a gram a side. That is usually a tenth of what the same panel would take in copper foil, and it is the single biggest practical difference between the two methods.

Estimating Seam Length

You do not have to measure every line. Lay a grid of n roughly equal pieces into a panel W wide and H high, and the total length of every solder line, borders included, comes out to:

Seam length = 2 × √(Panel area × Number of pieces) + W + H

That is exact for a grid and close enough for anything that is not deliberately lopsided. It is worth knowing where it comes from: the pieces have side s = √(area ÷ pieces), the panel holds H ÷ s horizontal lines and W ÷ s vertical ones, and adding the four outer edges leaves the formula above. Double the piece count and the seam length only goes up by about 40%, which is why a busy design costs far less extra solder than people expect.

Worked Example

A 30 × 40 cm copper foil panel with 35 pieces, beaded seams, intermediate cutter:

Panel area = 30 × 40 = 1,200 cm² Seam length = 2 × √(1,200 × 35) + 30 + 40 = 410 + 70 = 480 cm Front side = 480 × 0.55 = 264 g

Both faces get soldered, and the back takes roughly 60% of the front because you are filling rather than shaping a bead: 264 + (264 × 0.6) = 422 g, then a 15% intermediate waste buffer gives 486 g, or a little over one 1 lb spool.

An earlier version of this page used a lookup table of “density factors” that counted every seam twice, so it asked you to buy about double the solder you needed. The formula above agrees with the bead-volume method on the solder bead width page, which is the check that caught it.

Solder Types for Stained Glass

Waste Factor

Advanced hands lose about 10% to drips, tinning the iron and the odd rework. Intermediate 15%. Beginners should budget 25%, because learning to control the flow means a lot of solder ends up on the bench and back in the pot. Pick your level below and the buffer is applied for you.