How Much Fire Glass Do You Need for a Fire Table?
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Fire glass is one of those purchases that buyers almost always get wrong the first time — usually by buying too little. A sparse layer of fire glass sitting at the bottom of a deep burner pan looks cheap and exposes the burner, which defeats the purpose. Getting the fill right takes about five minutes of calculation, and it's worth doing before you order.
Here's the complete guide to calculating how much fire glass you need.
What Is Fire Glass?
Fire glass is tempered glass that has been tumbled to remove sharp edges, then coated with a heat-resistant reflective finish. It's designed to sit in the burner pan of a gas fire table or fire pit, fill the space above the burner, and reflect and refract the flame. The glass doesn't burn — it's tempered to withstand sustained heat — and it dramatically amplifies the visual impact of the flame.
Fire glass comes in sizes typically ranging from 1/4" to 3/4" diameter. Smaller sizes create a denser, more uniform look. Larger sizes catch and reflect more light individually. For most residential fire tables, 1/4" to 1/2" is the most common choice.
The Basic Formula
To calculate how much fire glass you need:
- Measure the length, width, and depth of your burner pan (in inches)
- Calculate the volume: Length × Width × Depth = cubic inches
- Convert to pounds: divide cubic inches by 100
This gives you the approximate number of pounds of fire glass needed to fill the burner pan to the top.
However, you typically don't want to fill the pan completely. You want the fire glass to sit about 1/2" to 1" above the burner, which keeps the glass visible while protecting the burner from direct contact with the glass. If your burner sits 2" from the bottom of the pan, you'd fill to about 3" deep rather than the full pan depth.
Worked Example
Say your burner pan is 30" long × 10" wide, the pan is 4" deep, and the burner sits 2" from the bottom. You want the glass to sit 1" above the burner, so you're filling to 3" depth.
30 × 10 × 3 = 900 cubic inches
900 ÷ 100 = 9 lbs of fire glass
Buy 10 lbs to account for settling and a generous fill level.
Common Fire Table Sizes and Approximate Fire Glass Needs
| Burner Pan Size | Fill Depth | Approximate Fire Glass Needed |
|---|---|---|
| 20" × 8" | 3" | 5 lbs |
| 28" × 10" | 3" | 8 lbs |
| 36" × 10" | 3" | 11 lbs |
| 48" × 12" | 3" | 17 lbs |
| 60" × 12" | 3" | 22 lbs |
These are estimates based on a 3" fill depth. Your actual pan dimensions may vary — measure before ordering.
How Thick Should the Layer Be?
The general guideline is to fill the pan so the fire glass sits approximately 1" above the burner ports. This is deep enough that the burner isn't exposed when the flame is on, but not so deep that you're wasting material or restricting gas flow.
Some burner designs specify a maximum glass depth — typically 2" to 3" above the burner. Check your fire table's installation documentation for this spec if it's listed. Going significantly deeper than recommended can reduce gas flow to the burner and affect flame performance.
Lava Rock as an Alternative
Lava rock serves the same function as fire glass at a lower cost. It fills the burner pan, distributes the flame, and protects the burner. Lava rock doesn't have the same reflective visual impact as fire glass — it reads as more natural and less decorative — but for buyers who prefer a simpler look, it's a practical choice.
The fill calculation is the same as fire glass. Lava rock is typically sold by the pound and covers approximately the same volume per pound as fire glass.
Mixing Colors
Mixing fire glass colors is common — a base of clear or black glass with an accent color on top is a popular approach that creates visual depth. When mixing, calculate the total volume needed and split the order accordingly. A common ratio is 70% base color, 30% accent color.
When to Replace Fire Glass
Quality tempered fire glass doesn't need to be replaced on any fixed schedule. It will fade slightly over years of use as the reflective coating degrades from sustained heat and UV exposure. When you notice the glass has lost its reflective clarity, replacement is straightforward — remove the old glass, rinse the pan, and refill with fresh material. Most fire glass is available in standard sizes from outdoor living suppliers.
Buying Fire Glass
Check your fire table manufacturer's documentation for any specific recommendations on glass size or fill depth. Most manufacturers specify the burner pan dimensions, which is all you need to do the calculation above.
Have questions about your specific fire table? Contact us — we can confirm the burner pan dimensions and recommended fill for any table in our fire table collection.