How this calculator works
The tray area times intended layer depth gives fill volume. American Fire Glass publishes a rectangular-tray coverage rule equivalent to volume in cubic inches divided by 19 for pounds required. That converts to about 1456.84 kg/m3 bulk density. Reflective coatings and recycled products do not establish a universal bulk density; choose custom coverage for another product.
Formula
V = tray area x layer depth; reference mass in lb = V in in3 / 19; custom mass in kg = V in m3 x bulk density; order mass = net mass x (1 + allowance).
Worked example
A 19 in by 10 in tray covered 1 in deep has 190 in3 fill volume. The manufacturer rule gives 10 lb, or 4.5359237 kg, before extra allowance.
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Frequently asked questions
Can I use ordinary glass?
Use glass approved by the burner and fire-glass manufacturer. A mass estimate does not establish heat resistance or appliance compatibility.
Why is the density lower than window glass?
A bed of fragments contains air gaps. The coverage equivalent includes these spaces; solid pane density does not.
How deep should the layer be?
Use the appliance and glass product instructions, particularly around burner ports and ignition components. The calculator does not choose a safe burner covering depth.