Lava Rock Calculator
A 10 ft by 10 ft bed at 2 inches is 0.62 cubic yards and 0.37 short tons at 720 kg/m³.
Last updated . 720 kg/m³ is a planning start inside a 40–50 lb/ft³ range published for one 3/4 inch black lava rock. 45 lb/ft³ is 720.83 kg/m³. One yard at 720 is 0.61 short tons, 1213.60 lb, and 0.55 tonnes. It is not a universal lab density and it is not pumice.
Heavier decorative stone belongs on the landscape rock calculator or the river rock calculator.
Lava rock bed
Planning start: 720 kg/m³, inside a 40–50 lb/ft³ product range for 3/4 inch black lava. 40 lb/ft³ is 640.74 kg/m³. 50 lb/ft³ is 800.92.
Volume and weight
Finished cubic yards
0.00
Order cubic yards
0.00
Order short tons
0.00
Order tonnes
0.00
Where 720 kg/m³ comes from
Gravelshop’s listing for 3/4 inch black lava rock states about 40–50 pounds per cubic foot (product page). Converted, 40 lb/ft³ is 640.74 kg/m³, 45 is 720.83, and 50 is 800.92. The field starts at 720 so it sits inside the range without pretending to be the exact midpoint. The range line uses 640 and 800, the rounded ends. FHWA loose pumice is a different material and is not the density here.
| Published end | kg/m³ | This 10×10×2 in bed |
|---|---|---|
| 40 lb/ft³ | 640.74, shown as 640 | 0.33 short tons |
| Start used here | 720 | 0.37 short tons and 0.34 tonnes |
| 50 lb/ft³ | 800.92, shown as 800 | 0.42 short tons |
Weight per cubic yard
One cubic yard at 720 kg/m³ is 0.61 short tons, 1213.60 lb, and 0.55 tonnes. At 640 it is 0.54 short tons and 1078.76 lb. At 800 it is 0.67 short tons and 1348.44 lb. Ordinary clean gravel at 1,600 kg/m³ is 1.35 short tons per yard, more than double.
Coverage
One cubic yard covers 162 square feet at 2 inches. A 10 by 10 foot bed is 100 square feet, so the volume is 0.62 cubic yards and 16.67 cubic feet. That volume is the same number a 1 inch gravel bed of this size would show. Only the tons change.
Worked example
Leave length and width at 10 ft, depth at 2 in, and density at 720. Finished and order cubic yards both read 0.62. Order short tons read 0.37. Order tonnes read 0.34. The range line reads 0.33 short tons at 640 kg/m³ and 0.42 short tons at 800 kg/m³. The formula line shows 16.67 ft³, 0.47 m³, allowance 0.00 percent, and 0.37 short tons at 720 kg/m³.
Frequently asked questions
How much does lava rock weigh?
A retail listing for 3/4 inch black lava rock gives about 40 to 50 pounds per cubic foot. That is one product’s range, not a lab value for every lava or scoria. 40 lb/ft³ is 640.74 kg/m³, 45 lb/ft³ is 720.83 kg/m³, and 50 lb/ft³ is 800.92 kg/m³. This calculator starts at 720 kg/m³, inside that range, not the exact 45 pound midpoint. One cubic yard at 720 is 0.61 short tons, 1213.60 lb, and 0.55 tonnes. One short ton is 1.65 cubic yards.
How much lava rock for 10 by 10 feet at 2 inches?
The bed is 0.62 cubic yards, 16.67 cubic feet, and 0.47 cubic meters. At 720 kg/m³ that is 0.37 short tons and 0.34 tonnes. The range line uses the finished volume: 0.33 short tons at 640 kg/m³ and 0.42 short tons at 800 kg/m³. The same 0.62 yards of ordinary 1,600 kg/m³ gravel would be 0.83 short tons. Lava is the light order.
Is lava rock the same as pumice?
No. FHWA’s earthwork tables list pumice much lighter than this, and that figure is not used here. Lava rock sold for beds is vesicular basalt or scoria. The 720 kg/m³ start comes from the 40–50 lb/ft³ band on one 3/4 inch black lava product page, not from the pumice row. Aquarium filter media that mentions lava stays on the aquarium gravel page.
Can I use lava rock on a driveway?
No. It is a decorative cover. It crushes under tires and it is far too light to read as a base. A driveway base belongs on the 304, 411, or crusher run calculator. This page will still multiply whatever area you type, and the tons will look small because the density is 720.
What size is landscape lava rock?
Bags are often sold as 3/4 inch, 1 inch, or a mixed decorative size. The density band cited here is specifically a 3/4 inch black lava listing. A different color or a larger scoria can sit outside 40–50 lb/ft³. Type the supplier’s number when you have it. Coverage at 2 inches does not change with the sieve: one yard still covers 162 square feet.
Why is the ton number so much smaller than river rock?
River rock on this site starts at 1,525 kg/m³, about twice 720. A 10 by 10 foot bed at 2 inches is 0.62 cubic yards either way. The lava weight is 0.37 short tons. The same shape in landscape rock at 1,500 kg/m³ would be near 0.78 short tons. Compare yards when you are buying by the yard, and tons when the yard sells by weight.
Does the tool add waste?
No. Finished yards and order yards both read 0.62. Allowance is 0.00 percent. Add a little yourself if the edging will scatter. The range line is the density band, not a waste percent.