What This Calculator Does
Fire glass is used to fill gas fire pits and fireplace burner pans in place of logs or lava rock. This calculator estimates how many pounds you need based on your fire pit’s shape, size, and desired fill depth.
The Formula
The fill volume is found from the burner area times the depth: for a round pit, area = π × radius²; for a rectangular pit, area = length × width. That area is multiplied by the fill depth to get volume, converted to cubic feet. Fire glass typically weighs around 100 lb per cubic foot when loosely filled, giving weight = volume (cu ft) × 100.
Manufacturers’ exact coverage rates vary by glass type and size, so check your specific product’s coverage chart, and always follow your fire pit or fireplace manufacturer’s minimum and maximum fill depth guidelines for safe operation.