Fire Glass and Lava Rock Quantity Calculators
How much fire glass do I need?
Measurements
Measure inside the pan. Fractions like 36 1/2 work.
Enter your measurements to see how much fire glass you need.
0lbs
0× 10 lb jars
Shop fire glassTotals round up to whole 10 lb jars. Check your burner manual for the recommended fill depth.
How much fire glass do I need? Quick answer
As a rule of thumb, you need about 7.6 lb of fire glass per square foot of pan for every inch of depth. For example, a 30-inch round fire pit needs about 37 lb for 1 inch of depth, or about 75 lb for 2 inches. Lava rock is lighter: about half the weight of fire glass for the same space.
Round fire pits: fire glass needed
| Inside diameter | 1 inch deep | 2 inches deep |
|---|---|---|
| 24 in | 24 lb (3 × 10 lb jars) | 48 lb (5 jars) |
| 30 in | 37 lb (4 jars) | 75 lb (8 jars) |
| 36 in | 54 lb (6 jars) | 108 lb (11 jars) |
| 42 in | 73 lb (8 jars) | 147 lb (15 jars) |
| 48 in | 96 lb (10 jars) | 192 lb (20 jars) |
Square and linear fire pits: fire glass needed
| Inside size | 1 inch deep | 2 inches deep |
|---|---|---|
| 24 × 24 in | 31 lb (4 jars) | 61 lb (7 jars) |
| 36 × 36 in | 69 lb (7 jars) | 137 lb (14 jars) |
| 48 × 12 in (linear) | 31 lb (4 jars) | 61 lb (7 jars) |
| 60 × 12 in (linear) | 38 lb (4 jars) | 76 lb (8 jars) |
For any other size, use the calculator above. Always measure the inside of the pan, not the outside of the fire pit.
Common questions
How do I calculate fire glass by hand?
Multiply the pan's inside area in square inches by the depth in inches, then multiply by 0.053 to get pounds of fire glass (or by 0.0265 for lava rock). For a round pan, the area is 3.14 × radius × radius.
How deep should fire glass be?
It depends on your burner and gas type, so always follow your burner manufacturer's manual. Propane burners generally need a thinner layer over the burner than natural gas burners.
Can I use lava rock underneath fire glass to save money?
Many people fill the lower part of the pan with lava rock and top it with fire glass. Check that your burner manual allows mixed media, and keep within its recommended total depth.
Why do you round up to whole jars?
Fire glass is sold in 10 lb jars, and it's better to have a little extra to level the surface than to run short.
How To Use The Calculators:
- Choose Fire glass or Lava rock, then the shape of your fire pit’s burn area. Linear pits use Square / rectangle / linear.
- Measure the inside of the pan and enter the sizes in inches or centimetres. The letters A, B and C match the drawing.
- Your total appears straight away, in pounds and in 10 lb jars or bags. Use the shop button to choose your colour or style.
The right fill depth depends on your burner and gas type, so check the coverage guidance below and your burner’s manual.
Information - Coverage
We strongly recommend consulting the manufacturer’s installation manual to ensure safety and optimize the burner’s longevity, as recommended fire media depths vary by brand.
Proper fire media coverage is crucial for even heat distribution, preventing hotspots that could damage the burner or fire pit structure. Additionally, the properties of propane and natural gas influence the maximum recommended depth of fire media above the burner.
- Generally, Propane fire pit burners should be covered with no more than 1 to 1.5 inches of fire media above the burner.
- For Natural Gas fire pit burners, the depth can be between 2 to 4 inches, although it’s best to use the minimum depth necessary for optimal performance.
Different burner styles affect the depth of fire media. For Jet or Nozzle Burners, such as Torpedo, Crossfire, and Bullet burners, the fire glass must not cover the tips. It should be level with the nozzles or slightly lower to ensure proper flame performance.
For more detailed information check out our article How to Use Fire Pit and Fire Place Glass.