How much Fire Glass do you need?  
It's Easy to calculate!

Most on-line calculators lead you to purchasing more fire glass than you'll actually need.  Its not very nice, but it is what they sell.  The minimum depth to fully cover the sand or crushed lava rock underneath is 1 1/2" to 2" deep.  That depth will provide a full covering and keep the glass quantity to a minimum. The best way to determine how much you'll need is to find out how many "square inches" you need to cover.  Below are formulas to help you determine the square inches.  Once you have the square inches, divide by 16 to get the number of pounds.  Since we sell fire glass in 5 pound bags, you'll round up or down to determine how many bags of glass you want to purchase.

Fireplace

Measure the front width, the width at the back.  Add together and divide by 2.  Multiply that number by the depth (front to back) to get the total square inches.  Divide that number by 16 to get the number of pounds.

Example:  Front width is 36", back width is 30" and the depth is 20".
36" + 30" divided by 2 = 33".  33" x 20" = 660" divided by 16 = 41 pounds

Rectangle Fire Pit

Measure the width (left and right) and the depth (front to back).  Multiply those two numbers to get the total square inches.  Divide that number by 16 to get the number of pounds.

Example:  Width is 36" & the depth is 24".
36" x 24" = 864" divided by 16 = 54 pounds

Round Fire Pit

Determine the diameter (the length across the opening at the widest part)
Half of the diameter is the radius
Multiply radius x radius x 3.14 to get the square inches
Divide the square inches by 16 = number of pounds you need
Example:  Diameter is 24", Radius is 12"
12 x 12 x 3.14 = 452 square inches divided by 16 = 28 lbs

Square Fire Pit

Just like the rectangle, measure the width (left and right) and the depth (front to back).  Multiply those two numbers to get the total square inches.  Divide that number by 16 to get the number of pounds.

Example:  Width is 24" & the depth is 24".
24" x 24" = 576" divided by 16 = 36 pounds