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Fire Glass Calculator

Created by Kenneth Alambra
Reviewed by Wojciech Sas, PhD and Steven Wooding
Last updated: Jan 18, 2024

This fire glass calculator, or fire pit glass calculator, will help you determine how much fire glass you need for your fire pit to look great. Determine the volume and weight of your needed fire glass quickly using this tool.

In this calculator, you will learn what fire glass is, how fire glass works, and how to calculate how much fire glass you need. Keep on reading to start learning.

What is fire glass? How does fire glass work?

If you like lighting a fire pit or a fireplace to warm your space instead of using a furnace heater, using a fire glass in your fire pit will definitely spark a conversation between you and your guests. Fire glass is an ornamental bead material that you can use to fill your fire pit as a replacement or add-on to other fire pit media like lava rocks, ceramic log sets, or ceramic river rocks.

An image of a fire pit with fire glass.

Note that we cannot use ordinary river rocks and ordinary glass as fire pit media because they could potentially explode in extreme heat. So only get fire glass from certified suppliers for your safety.

Like other fire pit media, we do not set fire glasses on fire. Instead, we use them to cover our fire pit's burner connected to a tanked fuel source like natural gas or propane. Fire glass consists of heat-tempered glass, which makes it able to withstand high temperatures, so it doesn't melt or break in an open flame.

A close-up image of reflective fire glass beads.

The main difference between fire glass and the other fire pit media is that fire glass can reflect and refract the light from the fire, giving off a sparkling appearance and attractive lighting in a room. If you need more serious lighting in your space, our lighting calculator will help you choose the correct number of bulbs to illuminate your area properly.

That sparkling feature, however, makes fire glass more expensive than other fire pit media. Since it's also made of glass, distributors add extra protection to their packaging, increasing its price even more. Because of that, we really should know how much fire glass we need, so we buy just enough for our fire pits.

🙋 If you only need to fill an ornamental pit that you won't set on fire, you can use river rocks or gravel instead. They are less expensive than fire glass but also come in different colors. Find out how much you'll need using our river river rock calculator or our Gravel calculator.

How much fire glass do I need?

Determining how much fire glass you need is very easy. All you have to do is to find the area you want to cover with fire glass. Then, multiply this area by how deep you want your fire glass cover to be. This way, we get the volume of fire glass we need, as also shown in this equation:

volume=area×depth\small \text{volume} = \text{area}\times \text{depth}

However, fire glass is usually available in terms of weight. You can then estimate how much fire glass you need by multiplying the volume you obtain by the density of fire glass, which is around 1.4 grams per cubic centimeter. In equation form, we express it as:

weight=volume×density\small \text{weight} = \text{volume}\times \text{density}

You can directly multiply this known density in grams per cubic centimeter if you measure your fire pit in centimeters. However, you may have to convert these units to suit your measurements. We have our density conversion and volume conversion tools you can use for that. Or you can simply use our fire pit glass calculator 🙂!

How to use our fire glass calculator?

Using our fire pit glass calculator is straightforward and intuitive. Here are the steps to follow when using our fire glass calculator:

  1. The first step is to select what fire glass type you want and purchase a recycled or reflective fire glass. Doing so will provide you with your selection's density for weight computation purposes.
  2. Then, select the shape of your fire pit or your fireplace.
  3. Enter your fire pit's dimensions in our fire glass calculator.

Upon entering the details above, we will provide you with the volume and weight of the fire glass you need for your fire pit or fireplace.

Sample fire glass calculation

Let's say we want to entirely fill a 60-cm square fire pit centerpiece that is 7.5 cm deep with recycled fire glass (density = 1.445 g/cm³). Since we can obtain the area of a square by multiplying its side measurement by itself, we get its area to be 60 cm * 60 cm = 3,600 cm². Then, we can calculate the volume using our equation:

volume=area×depth=3,600 cm2×7.5 cm=27,000 cm3\small \begin{align*} \text{volume} &= \text{area}\times \text{depth}\\ &= 3,600\ \text{cm}^2\times 7.5\ \text{cm}\\ &= 27,000\ \text{cm}^3 \end{align*}

Finally, we can determine how much fire glass we need in terms of weight, as shown below:

weight=volume×density=27,000 cm3×1.445 gcm3=39,015 g39.0 kg\small \begin{align*} \text{weight} &= \text{volume}\times \text{density}\\[0.5em] &= 27,000\ \text{cm}^3\times 1.445\ \tfrac{\text{g}}{\text{cm}^3}\\[0.5em] &= 39,015\ \text{g}\\ &\approx 39.0\ \text{kg} \end{align*}

We need about 39 kilograms of recycled fire glass to fill our fire pit based on our calculation above. Since fire glass costs roughly around $10 per kilogram, we may have to consider filling 5.0 cm of the fire pit with lava rocks first, then filling the remaining 2.5 cm with fire glass. That will leave us with just the third of the original quantity we need, bringing the cost down, too.

Nonetheless, fire glass may be expensive, but it will be worth it 🙂.


What is fire glass made of?

Fire glass is made of heat-tempered glass pieces and can also be coated with a reflective material to add excitement to your fire pit. It is not advised to experiment with using broken glass pieces as fire glass, even if the glass is from a broken tempered glass sheet. Obtain your fire glass from a certified supplier to be safe.

What is fire glass used for?

You can use fire glass primarily as fire pit media. Use it to fill a fire pit or a fireplace. Fire glass looks nice even when there is no flame, but it looks best when the burner is turned on. You can also use round polished fire glass as landscaping decoration. However, because fire glass is expensive, you might just want to get ornamental glass rocks for your landscape as they will be cheaper than fire glass.

How much fire glass should I use for a 60-cm square fire pit?

To know how much fire glass to use:

  1. Find the area of your fire pit in square centimeters: area = 60 × 60 = 3,600 cm².
  2. Multiply it by your desired fire glass cover thickness to get your needed fire glass volume in cubic centimeters. Let's say 5 cm: volume = 3,600 cm² × 5 cm = 18,000 cm³.
  3. Finally, multiply this volume to around 1.44 g/cm³ to find your needed weight in grams: weight = 18,000 cm³ × 1.44 g/cm³ = 25,920 g (or 25.92 kg).

Can I mix fire glass with lava rock?

Yes, you can pretty much combine fire glass with lava rock. However, if you want to lay your fire glass on top of your lava rock, installing an aluminum or steel wire mesh screen between the two layers would be the best way to do it. That way, when you want to separate the two materials in the future, it would be a lot easier.

Does fire glass burn on its own?

No. Fire glass is not flammable, and it is only used as a fire pit media to cover the burner mechanism of a fire pit. With that said, it would be best to cover the burner mechanism entirely of fire glass to effectively give the illusion that the fire glass is burning on its own.

Kenneth Alambra
Glass type
Reflective fire glass
Glass density
lb/cu ft
Fire pit shape
The illustration of a rectangular fire pit with its length, width, and thickness.
Glass dimensions
Length (l)
Width (w)
Depth (d)
cu in
Final output
Total weight
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