Calculating ‘How Much Fire Glass Do I Need?’ is not difficult, especially with the number of websites with a calculator available. Simply input the dimensions of your fire pit burn area into the calculator, follow the provided instructions, and it will estimate the required quantity in pounds.
However, what can make it slightly more complicated is the addition of lava rock as a filler in the base of the fire pit tray.
Why Use a Lava Rock Filler
We could dedicate an entire article to this topic, but the key takeaway is that using lava rock as a base in your fire feature helps the gas disperse more evenly.
This prevents the formation of damaging hotspots, especially when using larger fire media like ceramic fire stones or gas fire pit logs.
Additionally, lava rock filler contributes to a more natural-looking flame while being a cost-effective filler compared to fire glass, helping to reduce overall expenses.

The only exception to using filler is when you’re using clear glass in your fire feature. In this case, the dark rock could be visible through the glass, diminishing the clean and transparent aesthetic of the glass. In this instance, you should use only the glass to fill the pan.
Lava Rock Filler Depth
The filler layer should fully cover the burner, with a minimum depth of at least 1/4 inch above it to ensure proper coverage and optimal performance.
Glass Depth
We recommend consulting the burner manufacturer’s installation guide to ensure you stay within the maximum recommended depth for safe and efficient operation. Keep in mind that the maximum fire media depth may differ depending on whether you are using natural gas or propane.
While a flat, level finish, flush to the top of the tray is common, you might prefer mounding the glass from the edges toward the center; just be sure to stay within the recommended depth limits and be aware this may alter the flame aesthetic.
Please note that if using Crossfire, Torpedo, or Bullet Burners the jets should not be buried.
The advantage of using a drop-in style pan is that the design minimizes the quantity of fire media needed, helping to keep costs down. Here at The Magic of Fire, the pan depth generally ranges between 2 to 2 1/2 inches, providing the perfect balance between functionality and efficiency.
The pans are available in kit form with spark ignition, electronic ignition, flame-sensing safety technology, and more!

Calculating Fire Pit Glass
The critical factor is that the glass is about twice as dense as lava rock and provides only half the coverage. This is the reason why using lava rock filler is so economical—not only is it cheaper per lb, but it also provides twice the coverage!
Due to the information above, the calculations for the different types of fire media must be done separately. This is where calculators are really helpful! We offer two different calculators: one for lava rock and one for fire pit glass.
- You will need the dimensions of the burn area to be filled with your chosen fire media; the length, width, or diameter if the fire feature is round.
- You will need the intended depths of the fire media.
Glass Only
- You will need the overall depth; from the base of the burn area up to the level recommended by the manufacturer for the burner.
- Using the fire glass calculator, enter the dimensions.
Lava Rock Only
- You will need the overall depth; from the base of the burn area up to the level recommended by the manufacturer for the burner.
- Using the lava rock calculator, enter the dimensions.
Using a Filler layer
You will need to perform two separate calculations, one for each layer, using the measured fire media depths as described below:
- Filler Depth: Measure from the base of the burn area up to 0.25 inches above the burner. This gives you the depth of the lava rock filler.
- Glass Depth: Calculate the depth of the glass media by subtracting the 0.25-inch filler from the recommended maximum depth above the burner.
How Much Fire Glass Do I Need? – Conclusion
The calculators will provide the quantity of fire media measured in pounds (lbs). At The Magic of Fire, most fire media is sold in 10lb bags, making it easy to determine the quantity needed for your fire feature.