Landscape Rock Calculator
Estimate decorative or drainage rock from the area and depth. Get the volume in cubic yards, the weight in tons for bulk delivery, and the bag count — with the density set to your rock, since river rock and lava rock weigh very differently.
2 in for small stone and top-ups; 3–4 in for larger rock or coverage.
Rock density varies a lot — confirm the weight per yard with your supplier. Leave bag blank for bulk only.
Advanced: price
Formula & how it works
Volume = area × (depth ÷ 12) cubic feet; cubic yards = ÷ 27.
Weight = cubic yards × weight per yard, shown in tons (÷ 2,000). Bags = cubic feet ÷ bag volume, rounded up.
Worked example
A 20 × 10 ft area (200 ft²) at 3 in of river rock is 50 ft³, about 1.85 cubic yards. At 2,700 lb/yd³ that's roughly 2.5 tons — how bulk rock is priced. Switch to lightweight lava rock at 1,400 lb/yd³ and the same volume weighs under a ton, which changes delivery entirely.
Ordering rock
Density is the whole story for weight
Landscape stone is sold by the ton as often as by the yard, and the two are linked by density — which varies enormously. Dense river rock and crushed stone weigh nearly twice what airy lava rock does for the same volume. Pick your rock type to start, then confirm the weight per yard with the supplier, because even "river rock" ranges by size and source.
Depth follows the stone size
Small decorative stone reads well at about 2 inches, while larger cobble and rock meant to suppress weeds or handle drainage want 3 to 4 inches so the ground doesn't show through. Deeper layers scale the volume and the tonnage directly, so the depth you choose has real cost — set it to the stone and the job, not by habit.
Bulk versus bags, and a base
Bagged rock suits small features and tight access; bulk by the ton is far cheaper once you're moving any real quantity. For paths and areas that carry foot traffic, rock usually goes over a compacted base and landscape fabric rather than bare soil — that's separate material, but worth planning for alongside the stone.