Choose the finish
Which decorative rock belongs in this space?
Decorative rock is a visible finish, so start with the place it will be seen and touched. Size, shape and color affect how the bed looks and behaves; those details also determine the depth you should confirm with the seller. The calculator handles the order quantity after you choose that depth.
Marble chips
Angular, light-colored chips give strong contrast in a border or modern bed. Check the actual chip size and bag volume, and expect to remove leaves if you want the light surface to stay clean.
Calculate marble chips →Lava rock
Porous red or black pieces give a different texture and often a lighter load for the same bed volume. The loose weight varies widely between products, so confirm it before ordering by the ton.
Calculate lava rock →Beach pebbles
Smooth, rounded pebbles suit a contained accent area or water feature. Check the size grade and the seller's coverage chart. Rounded stones may move under frequent footsteps.
Calculate beach pebbles →For a mixed, naturally rounded look, compare river rock. For a broader material estimate across bed shapes, use the landscape rock calculator.
Measure the bed
Turn surface area into an order quantity
- Measure the stone footprint. Use length × width for a rectangle. Split an L-shaped border into smaller rectangles and add them. Subtract paving or other ground you will leave uncovered; a shrub canopy alone does not remove the ground beneath it.
- Choose the installed depth. A 2–3 inch layer is a common starting range for inorganic mulch, but larger stones and the exact look you want may call for a different depth. Check the product's coverage guidance. For an existing bed, enter only the missing depth of a top-up.
- Calculate volume, then ordering units. Square feet × inches ÷ 12 gives cubic feet; divide by 27 for cubic yards. Enter the supplier's loose weight to estimate US tons. Divide cubic feet by the bag's labeled cubic-foot volume and round up.
- Compare the quote. Ask whether the yard sells by cubic yard, short ton, bag or pallet; check its minimum increment and delivery charge. Check your vehicle's payload before choosing pickup.
At 100 sq ft and 3 in, base volume is 25 ft³ = 0.93 yd³. With a 10% allowance it becomes 27.5 ft³ = 1.02 yd³, or 55 bags at 0.5 ft³ each. At the editable 1.35 ton/yd³ example, the buffered load is about 1.38 US tons. A bag labeled 0.25 ft³ would require 110 bags for that same buffered volume.
Depth guidance: Utah State University Extension recommends 2–3 inches for inorganic mulch; Beach Pebbles Direct uses 2 inches for most of its pebble projects. See the rock depth guide for a closer look at stone size and use.
Understand the estimate
Why a weight preset is only a starting point
The same 0.93 cubic yard fills a 100 sq ft bed at 3 inches no matter which stone is selected. The tonnage changes with the product's loose bulk weight. The calculator starts at 1.30 US tons per cubic yard for mixed decorative rock, 1.35 for marble chips (2,700 lb) and 0.75 for lava rock (1,500 lb), all editable. Sunshine Coast Materials gives a 1.30–1.45 tons-per-yard range for its decorative stone. Cummin Landscape Supply lists about 2,700 lb per cubic yard for its marble chips. Lava rock is lighter and varies too: Landscape Centre lists 1,250 lb per yard, while Kentucky Lawn Care lists 1,500 lb. Replace each preset with the loose weight for the product on your quote.
Bag volume is equally product-specific. Vigoro marble chips are labeled 0.5 ft³ and 50 lb; a Rain Forest beach pebble bag is labeled 0.25 ft³ and 20 lb. Those labels describe different products. If a package only gives square-foot coverage at a stated depth, use that exact product coverage to check the quantity before purchase.
Plan the finished bed
Where the stone goes matters as much as how much you buy
Keep it contained
Use a defined edge where rock meets lawn, paving or loose soil. Place and level the material in sections so the finished layer matches the depth you entered, rather than piling all material near the delivery point.
Give plants room
Keep the rock off stems and trunks. Rock can heat a planted bed in full sun, and a stone layer does not add organic matter. Colorado State University Extension discusses site-dependent rock mulch effects; Utah State recommends organic mulch around trees.
Expect maintenance
Rock reduces some light at the soil surface but cannot guarantee a weed-free bed. Remove fallen leaves and soil that collect in gaps, especially along edges. UC IPM notes that weeds can exploit fabric gaps. See weed control for rock beds.
Building a path or vehicle surface? Decorative top stone is only one layer. Use the driveway calculator for a load-bearing project. For the complete bed sequence, see how to install landscape rock.
Continue with the material-specific guide
Decorative rock questions
How much decorative rock do I need for 100 square feet?
At a finished depth of 3 inches, 100 square feet needs 25 cubic feet, or about 0.93 cubic yard, before any extra material. At the mixed-stone planning weight of 1.30 US tons per cubic yard, that is about 1.20 US tons. A 0.5-cubic-foot bag count is 50; verify the actual bag label.
Does one ton of lava rock cover the same area as one ton of marble chips?
Usually no. Area and depth set the volume, while loose bulk weight determines how many tons fill that volume. The calculator uses editable examples of 0.75 US ton per cubic yard for lava rock and 1.35 for marble chips. Supplier figures can differ.
Can I assume every decorative rock bag is 0.5 cubic foot?
No. Bags are sold in different volumes and weights. Enter the cubic-foot volume from the product label. If only square-foot coverage is listed, use it to cross-check the result at the label’s stated depth; do not assume that a 20-pound bag contains the same volume as a 50-pound bag.
Will rock and landscape fabric stop all weeds?
No. A suitable rock layer can reduce light reaching the soil, and fabric may help in some sites, but windblown soil and organic debris can collect above the rock and support new weeds. Plan to remove debris and inspect edges.