LANDSCAPE ROCK
Landscape rock calculator
Cubic yards of landscape rock = square feet × depth in inches ÷ 324, and cubic feet = square feet × depth in inches ÷ 12. Landscape rock is sold in cubic yards, in bags, and sometimes by the ton — the volume is what you calculate first, and everything else is a conversion from it.
Worked example
A 250 sq ft bed at 2 inches: 250 × 2 ÷ 12 = 41.67 cubic feet, and 250 × 2 ÷ 324 = 1.54 cubic yards.
In bags, divide by the bag volume the product states and round up. Bags of decorative rock are commonly sold by weight rather than volume, so the volume per bag is the number to find on the label — a bag sold by weight tells you nothing about coverage until you have its cubic feet.
When the supplier quotes by the ton
Decorative rock is frequently priced by the ton, and the coverage that a ton gives depends on the rock. One supplier's published technical page states its coverage basis plainly and narrowly:
“coverage per ton is based on 1”-2” depth.”
Buckingham Slate, hardscapes brochure, read 2026-09-21.
Read that carefully: it is a coverage-per-ton figure, and it is only valid at a stated depth. Order a ton of the same rock at 3 inches and the covered area changes, because a ton is a weight and coverage is a volume. If a quote comes in tons, ask for the pounds per cubic yard for that specific product — density varies by rock type and gradation, and a borrowed density can be far enough out to change the load count.
Volume stays the reliable basis. Convert your area and depth to cubic yards, then ask the supplier to price it in cubic yards or to give you their own conversion.
Published figures you can check your quote against
| Figure as published | Source (read 2026-09-21) |
|---|---|
| “coverage per ton is based on 1”-2” depth.” | Buckingham Slate, hardscapes brochure |
| “Coverage is based on approximately 0.675 cubic feet per 90 lb bag for concrete applications.” | KRC Rock, Apache Brown product page |
| “Waste 5% Simple Layout 10% Standard Layout 15% Cuts / Pattern 20% Complex Layout” | KRC Rock, Apache Brown product page (waste allowance table) |
That second line is the useful one for anyone ordering bagged rock: a 90 lb bag at 0.675 cubic feet means 40 bags to a cubic yard, on that supplier's own figure. And the third line answers a question most calculators ignore — the waste allowance, which on that page runs from 5 percent for a simple layout to 20 percent for complex cuts. Work out your volume first, then add the allowance you decide, once, at the end.
Depth and containment
Depth is a design decision: a decorative dressing, a dry creek bed and a border that will be walked on are three different depths, and rock is heavy enough that ordering too deep is expensive to undo. Two practical points that do not change the volume:
- Weed membrane under decorative rock keeps soil from migrating up through it. It does not change the cubic yards you order.
- Edging matters even more than it does for gravel — rock rolls and spreads unless something contains it.
Ordering checklist
- Net area in square feet, with paths and planting gaps removed.
- Depth in inches, chosen for the design.
- The product name. “Landscape rock” covers a wide range of stone, and they do not weigh or cover the same.
- Whether the quote is in yards, bags or tons — and if tons, the density the supplier is using.
- Waste allowance, decided once and applied to the total.
Related calculators
Gravel calculator for the general aggregate case and the tonnage method · Pea gravel calculator · Mulch calculator for the same volume arithmetic.
Sources, all read directly on 2026-09-21: Buckingham Slate, L-Series landscaping aggregates brochure, buckinghamslate.com. KRC Rock, Apache Brown product page, krcrock.com. Both are supplier technical pages stating their own figures; neither is a standard, and neither applies to another supplier's rock.
Cite this dataset
The mulch coverage, bag-count and dated price tables from this site are archived as a citable dataset: Mulch coverage, bag-count and dated bulk price tables, version v1, published 20 September 2026, 9 files, creator ERTHK — DOI 10.5281/zenodo.22855990, record at zenodo.org/records/22855990.
Released under CC0 1.0 Universal (Creative Commons Zero v1.0 Universal): free to copy, modify and redistribute.
The source library that generates the tables, with its test suite, is at github.com/ERTHK/mulch-measure-calculator-kit, released under the MIT license.