Lead Came ↔ Glass Thickness Converter
Match H-channel or U-channel came to your glass or look up what a came size fits.
If your panel just mixes different single layer thicknesses, don't check this — enter only the thickest piece below; thinner pieces get shimmed with cement.
H channel vs U channel: which do I need?
H channel has a channel on both sides so it holds two adjoining pieces of glass together that's the interior seams of a panel. Round profile H came is the usual choice there because it doesn't pucker on curved lead lines the way flat lead does.
U channel has a channel on one side only so it wraps a single edge that's the border around the outside of a panel. Flat H came is also commonly used as a border/structural lead instead of U and if the panel is going into an existing frame, installers often prefer H at the outer edge since it leaves room to trim or adjust later.
Border came is often sized larger than the glass strictly needs that extra channel is margin for measuring and fitting error not a glass thickness requirement.
What do Channel, Face, Width & Heart Thickness mean?
- Channel (Heart depth): the internal slot depth the glass slides into the number that must match your glass thickness.
- Face (Leaf): the visible width of the lead line from the front.
- Width: the total width of the came's cross section.
- Heart thickness: the thickness of the central web between the glass pieces (H) or against the glass (U) this is what gives the came its strength.
Separately from channel depth: pattern cutting conventionally adds a 1/16″ allowance per came heart when cutting the glass pieces themselves — that affects the cut size of the glass not which came size to pick.
"Channel depth ≈ glass thickness + 1.5–2mm clearance" is a trade rule of thumb corroborated by multiple suppliers, not a published engineering spec — treat close matches as good fits not exact science.
The Lead Came to Glass Thickness Converter matches your glass to the right came profile in either direction.
Enter a thickness and it returns which H channel or U channel size fits, ranked by best fit or start from a came size and get the glass range it holds.
Hobbyists piecing together a first sun catcher and studio artists pricing a commissioned window both get a plain answer instead of a guess pulled from an old catalog.
What the Converter Does and What Problem It Solves
Picking lead came by eye is how panels end up loose in the channel or cracked because the heart never had room to seat the glass without binding.
This converter runs on a trade rule of thumb the stained glass supply trade has used for years: channel depth should land at glass thickness plus 1.5 to 2mm of clearance.
It also checks your thickness against five reference bands, from thin 3/32 inch single strength sheet up through triple fused slabs and flags when a job calls for a wide, high heart profile instead of a standard one.
A bare clearance formula would give you a depth number without telling you if a normal profile can reach it.
Thicker fused pieces and plated glass often need a high heart came and the converter catches that before you order lead too shallow to hold the piece.
How to Use the Converter, Step by Step
Start on the Glass to Came Size tab and type in your glass thickness, choosing mm or inches.
The preset buttons for 3/32, 1/8, 3mm fusible, 3/16, 1/4 and 3/8-plus save you retyping common sizes. Use the profile dropdown to narrow results to round H, flat H, round U, flat U or metric high heart or leave it on all profiles.
If your panel uses plated glass, two sheets leaded together as one piece, check that box and enter the second layer's thickness.
Don't check it just because a panel mixes different single-layer thicknesses in different spots; enter only the thickest piece since thinner pieces get shimmed with cement instead.
Switch to the Came Size to Glass Range tab if you already have came on hand and want the thickness it holds.
Measuring Glass Thickness Correctly
Measure with a caliper rather than trusting a supplier's spec sheet number since sheet glass commonly runs a few tenths of a millimeter off its nominal rating. Check more than one spot especially with hand rolled or textured art glass, where thickness shifts edge to edge.
How to Read Your Results
The top result shows your required channel depth in mm and inches, the minimum heart depth a came needs to hold your glass without binding.
Below that, a reference band label names the glass category matched such as standard 1/8 inch art glass or double fused 1/4 inch work and whether it calls for a high heart profile.
Each profile group shows a best fit card and an also works alternative, with channel, face, width and heart thickness listed for each.
The gauge bar under each card shows how much channel room that came has against your project.
On the reverse tab, picking a came size returns a glass thickness range rather than a single number, since a channel snug on one end and roomy on the other is still workable.
Who This Converter Is Built For
Hobbyists building their first leaded panel get the most obvious use here since choosing between round H, flat H, round U and metric high heart with no frame of reference is where beginners guess wrong.
Studio artists quoting a client job benefit just as much, especially when a design mixes glass thicknesses and needs different came for interior seams versus the border.
Restoration techs matching new came to an existing antique window lean on the reverse tab, since old came is often stamped with a size but not the glass range it was cut for.
If you're stocking supplies for other handwork alongside a glass project, SpeedCalcs Crafts & Fabric calculators cover quilting, candle making and more with the same plain number approach.
Real World Use Cases and Practical Tips
Say you're building a first sun catcher out of 3mm fusible glass. Tap the 3mm preset, leave the profile filter on all and the converter points you toward a round H sized for interior seams with room to spare, no plated box needed.
That's the difference between guessing at a lead came heart size for glass thickness and having a number before you cut a single piece.
Now say you're patching an antique window where the original panel used two thin layers leaded together as one plated piece.
Check the plated box, enter both thicknesses and the combined stack pushes you into high heart territory even though neither sheet alone would need it.
Treat every result as a trade rule of thumb rather than an engineering spec; glass and hand stretched lead both vary from their packaged ratings.
Lead Came Size Chart FAQ
What is the difference between H channel and U channel lead came?
H channel has a channel on both sides and joins two adjoining pieces of glass, which is why it's the standard choice for interior seams. U channel has a channel on one side only, wrapping a single edge as border came.
What size lead came do I use for stained glass panels?
It depends on where the came sits and how thick your glass is. Interior seams typically take a round H sized to glass thickness plus clearance while borders run a size up for fitting error, so run your actual thickness through the converter rather than guessing from a general lead came size chart.
What's the standard channel size for lead came, like 3/16 vs 1/4?
There isn't one universal standard since sizing varies by manufacturer and by whether the came sits in an interior seam or a border. A 3/16 inch profile usually suits single-layer art glass in the 4 to 5mm range while 1/4 inch and larger sizes show up on plated or heavily fused work, and glass thickness is what decides which one you actually need.
Run your glass thickness through the converter before you place a came order not after and you'll spend less on returns and shimming cement over a project's life.
The result is a real channel depth number, matched against actual profile dimensions, instead of a lead came size chart pulled from a general catalog.
