Landscape Rock Coverage Calculator

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Project preset:

Choose the closest job, then replace the sample measurements with the site takeoff.

Area source:

Measured area is best for curved beds and plan takeoffs.

Bed length and width:

Length × width; both values share the selected unit.

Outside diameter:

Measured rock area:

Installed depth:

Rock type:

Profile densities are planning values, not supplier specifications.

Bulk density:

Reserve / settling:

Supplier sells by:

Supplier order increment:

Bag weight:

Price per supplier unit:

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Estimate landscape fabric:

The neutral default is off; fabric does not change the rock quantity.

Fabric roll width:

Use the roll width printed on the fabric label.

Fabric overlap:

Zero is neutral; add only the seam and edge allowance you plan to use.

Delivery capacity:

The neutral default is 0; confirm any capacity with the supplier.

Item	Estimate	Order	Basis	Copy
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Check	Status	Detail	Action	Copy
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Rock type	Density	Coverage at depth	Best use	Copy
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A rock order has to fill a three-dimensional layer, even when the project begins as a flat bed measurement. Area establishes the footprint, installed depth turns that footprint into volume, and loose bulk density converts volume into weight when the supplier sells by the ton or tonne.

Depth usually changes the order faster than small measuring errors. A 100 mm layer needs twice the volume of a 50 mm layer over the same bed. Rock size and shape also matter because rounded gravel, angular stone, decomposed granite, and lightweight lava rock do not pack to the same loose density.

Area: The finished rock footprint, excluding patios, trunks, structures, and other uncovered spaces.
Depth: The average installed layer, not simply the largest stone dimension.
Bulk density: Loose material weight per volume. A supplier value is preferable to a generic profile.
Reserve: Extra quantity for grade variation, settlement, edges, and touch-up rather than a uniformly deeper layer.

Supplier units determine the final rounding. Bulk yards, cubic metres, tons, and tonnes may be sold in fixed increments, while bagged material must be rounded to whole bags. The order should therefore be rounded only after reserve and density have been applied.

Coverage estimates cannot settle drainage design, slope stability, edge restraint, weed control, plant health, or vehicle loading. Those decisions depend on the site and the selected material, and they should be checked separately before delivery.

How to Use This Tool:

Measure the finished footprint and confirm how the supplier quotes the exact rock before choosing an order quantity.

Select the Area source, then enter a rectangle, an outside diameter, or a measured rock area. Exclude spaces that will not receive stone.
Enter the average Installed depth. Use the depth slider to compare reasonable layers rather than measuring only the deepest point.
Choose a Rock type for planning or enter the supplier's loose Bulk density. The supplier value should replace the profile when available.
Set Reserve / settling, the supplier selling unit, order increment or bag weight, and optional price. Bulk quantities round up to the entered increment; bag orders round up to whole bags.
Open Advanced only when fabric overlap or delivery capacity needs an estimate, then review Order takeoff with the depth, density, rounding, and delivery checks before placing the order. Fabric does not change the rock quantity.

Interpreting Results:

The recommended supplier order is the rounded purchase quantity, not the exact geometric need. Compare the exact and rounded amounts to see how much of the difference comes from reserve and how much comes from the supplier's selling increment.

Depth fit compares the entered depth with the planning band for the selected rock profile. A warning is a prompt to confirm stone size and intended use, not a universal installation rule.
Density source deserves priority when ordering by weight. Moisture, grading, compaction, and the supplier's loose-volume method can all move the real figure.
Delivery loads are useful only when the entered truck capacity matches the supplier's actual vehicle and access limits.

Technical Details:

All geometry is converted to metres and square metres before volume is calculated. Weight-based orders then use kilograms internally, while volume-based orders retain cubic metres until the selected supplier unit is applied.

Formula Core:

The calculation builds from footprint area to exact volume, reserve-adjusted volume, and loose material mass.

\begin{aligned} A_{rectangle} & = L \times W \\ A_{circle} & = π \times {(\frac{D}{2})}^{2} \\ V_{exact} & = A \times d \\ V_{order} & = V_{exact} \times (1 + \frac{r}{100}) \\ m & = V_{order} \times ρ \end{aligned}

Landscape rock formula symbols
Symbol	Meaning	Canonical unit
`L`, `W`, `D`	Bed length, width, and outside diameter	m
`A`	Finished rock footprint	m²
`d`	Average installed depth	m
`r`	Reserve or settling allowance	%
`ρ`	Loose bulk density	kg/m³
`m`	Reserve-adjusted rock mass	kg

For a 24 m² bed at 50 mm, exact volume is 1.20 m³. A 10% reserve raises the order volume to 1.32 m³. At 1,602 kg/m³, the loose mass is 2,114.64 kg; a supplier selling metric tonnes in 0.1-tonne increments produces a 2.2-tonne order.

Lookup Core:

The rock profiles are editable planning values. Use the quoted loose bulk density and depth specification for the actual material when available.

Landscape rock planning density and depth profiles
Rock profile	Density	Planning depth
Pea gravel	1,661 kg/m³	50 to 100 mm
River rock, 1 to 3 in	1,602 kg/m³	50 to 100 mm
River rock, 3 to 5 in	1,483 kg/m³	75 to 150 mm
Crushed stone or limestone	1,721 kg/m³	75 to 150 mm
Decomposed granite	1,780 kg/m³	50 to 100 mm
Lava rock	949 kg/m³	50 to 75 mm
Marble chips	1,661 kg/m³	50 to 75 mm

Rule Core:

Landscape rock planning status and rounding rules
Decision	Rule	Meaning
Below profile band	Depth is less than the profile minimum	Confirm coverage and stone size
Within profile band	Depth is at least the minimum and no more than 135% of the profile maximum	Depth remains inside the planning acceptance range
Above profile band	Depth is greater than 135% of the profile maximum	Review excess material, grade, and intended use
Reserve status	Below 8% is low; 8% through 20% is typical; above 20% is high	Planning signal only
Order rounding	Always rounds upward to a whole bag or entered bulk increment	Prevents an order below the modeled need

Fabric area equals the footprint multiplied by its overlap allowance, and roll length equals that area divided by roll width. Delivery load count rounds the reserve-adjusted mass upward against the entered truck capacity.

Accuracy Notes:

The arithmetic is deterministic, but the physical inputs are estimates. Average depth, irregular boundaries, slopes, settled subgrade, moisture, and material gradation can dominate the final error.

Measure separate zones when depth or material changes across the site.
Ask whether the supplier density represents loose, compacted, wet, or dry material.
Confirm minimum orders, increments, load limits, delivery fees, and access before purchase.
Treat the profile depths and densities as planning values; the supplier and site specification take precedence.

References:

Mulching, Colorado State University Extension.
Mulches, University of California Statewide Integrated Pest Management Program.