What Is the Fire Glass Calculator?
Fire glass is tempered, tumbled glass used in fire pits, fireplaces, and gas fire features instead of lava rock or ceramic logs. Buying the right amount matters: too little leaves bare burner ports exposed, while too much wastes money and can smother the flame. This calculator estimates how many pounds of fire glass you need based on the surface area of your fire feature and the depth of glass you want to lay.
How to Use It
Measure the inside opening of your fire pit or pan in inches — the length and the width. Then choose the depth of glass you want; most installers recommend 1–2 inches for decorative cover, and a bit more if you want to fully conceal the burner. Enter the three values and the calculator returns the recommended weight in pounds.
The Formula Explained
First the calculator finds the surface area in square feet by multiplying length × width (in inches) and dividing by 144 (since 12 in × 12 in = 144 in² = 1 ft²). It then multiplies that area by the glass depth in inches and by an average coverage factor of 1.25 lbs per ft²-inch. Fire glass density varies by piece size and color, so treat the result as a close estimate and round up when ordering.
$$\text{Weight (lbs)} = \frac{\text{Length (in)} \times \text{Width (in)}}{144} \times \text{Depth (in)} \times 1.25$$
Worked Example
A square fire pit measuring 24 in × 24 in with 2 in of glass: area = \((24 \times 24) \div 144 = 4\ \text{ft}^2\). Weight:
$$\text{Weight} = 4 \times 2 \times 1.25 = 10\ \text{lbs}$$So roughly 10 pounds of fire glass would fill that pit two inches deep.
FAQ
How deep should fire glass be? A 1–2 inch layer is typical for looks; aim to cover the burner by about ½ inch so the flame still breathes.
Is the result exact? No — glass density differs by product, so order slightly more to be safe.
Does this work for round fire pits? For a circle, enter the diameter as both length and width; the result will be a small over-estimate, which is usually fine.
