Lava Rock Calculator — How Much Lava Rock Do You Need?
Pre-set for lava rock at ≈0.7 tons per cubic yard — roughly half the weight of normal gravel. Enter bed dimensions and depth for instant yards, tons and bags.
Gravel calculator
Density shown is an industry-typical value and varies by supplier — confirm before ordering.
You need
Includes +10% extra
36.0
cubic feet
1.33
cubic yards
1.87
tons (2,000 lb)
72
bags (0.5 cu ft)
≈ 0.76 m³
Estimated cost: $0.00 (at $0/ton)
Order 5–10% extra for compaction and settling — loose gravel always settles to less volume after compaction.
How much lava rock do you need? Multiply coverage area by depth in feet, divide by 27 for cubic yards, then multiply by about 0.7 to get tons. One cubic yard of lava rock covers roughly 160 square feet at 2 inches and weighs only about 1,400 lb — half of standard gravel. A 200 sq ft bed needs 1.25 cubic yards, or 0.88 tons.
What is lava rock?
Lava rock (also called scoria) is porous volcanic stone, full of gas bubbles, sold in red, black and brown tones for decorative landscaping. Those bubbles make the stone startlingly light — about 0.7 tons per cubic yard versus 1.35–1.6 for dense gravels — and give it a rough, pumice-like texture that grips soil. Common sizes are 3/4 to 1-1/2 inches. It is decorative through and through — the porous structure crushes under real loads, so it never appears in driveways or structural bases.
Best uses and recommended depth
Install lava rock 2 inches deep in planting beds — 3 inches only over bare, weedy ground — always over landscape fabric.
- Xeriscape and desert-garden beds — 2″; the classic pairing with succulents and agave.
- Fire pits and fire features — heat-safe as surround filler.
- Roof gardens and containers — 1–2″ where weight budget rules out dense river rock.
Keep lava rock off paths and patios you actually walk on: it is brittle underfoot and unpleasant barefoot. For walking surfaces see pea gravel or decomposed granite.
Pros and cons of lava rock
Lava rock wins on weight, permanence and bold color — and loses on comfort, handling grit, and any structural use.
Pros
- Half the weight of other gravels — haul and spread it easily
- Insulates soil and slows moisture loss in hot climates
- Won't rot, blow away, or attract pests (unlike mulch)
Cons
- Crushes under foot and wheel traffic — decorative only
- Dusty, gritty to handle; wear gloves
- Hard to clean leaf litter from between pieces
- Removing or changing it later means picking pieces out by hand
Lava rock price: what to expect
Typical published US prices put bulk lava rock around $60–$150 per ton or $45–$110 per cubic yard — the per-yard price beats dense stone because you are buying air as well as rock. Bags (0.5 cu ft) cost several times bulk rate per yard; red tends to price below premium black. Compare bids per cubic yard, not per ton — with density at 0.7 tons/yd³, a ton of lava rock is a third more material than a ton of crusher run. The calculator's per-yard cost mode handles exactly that comparison.
Frequently asked questions
How deep should lava rock be in landscaping?
A 2-inch layer covers planting beds well; 3 inches improves weed suppression on bare soil. Lava rock is lightweight and stays put once placed, so extra depth adds cost faster than benefit.
How much does a yard of lava rock weigh?
Only about 0.7 tons (1,400 lb) per cubic yard — roughly half the weight of typical gravel — because the stone is porous. One cubic yard covers around 160 square feet at 2 inches deep.
Is lava rock good for driveways or paths?
No — lava rock is decorative. Its porous, fragile stones crush under vehicle or foot traffic, so use it for beds, fire features and accent areas. For driving or walking surfaces choose crushed stone or pea gravel.