Landscape Rock Calculator
Use this Landscape Rock Calculator to estimate decorative rock for a rectangular planting bed, border or ground-cover area.
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How to Use the Landscape Rock Calculator
Enter bed length, width and planned rock-layer depth. Choose feet/inches or meters/centimeters. Use the supplier’s loose bulk density, or an illustrative editable density preset, and add an optional waste allowance. Read volume and weight together when requesting a supplier quote.
Formula and Explanation
Base volume = bed length × bed width × layer depth Order volume = base volume × (1 + waste / 100) Order weight = order volume × loose bulk density Cubic yards = cubic feet ÷ 27 Metric tonnes = kilograms ÷ 1,000; US short tons = pounds ÷ 2,000
A layer estimate spreads volume uniformly across the measured rectangle. Density accounts for the rock and void spaces together. Different sizes, shapes and packing can change coverage and bulk density even for similar stone. The presets are low/middle/high arithmetic examples, not product-specific density claims.
Choose depth with the actual rock size and intended appearance in mind; a calculated average depth does not guarantee that large stones cover every gap. Borders, stepping stones, plant openings and irregular shapes require separate measurement adjustments. Landscape fabric is a separate design choice: consider permeability, soil contact, planting and later maintenance rather than assuming it is always needed. No bag count, freight cost or weight certification is provided.
Worked Example
A 4 m × 2 m bed with a 5 cm layer needs 0.4 m³ before allowance. At 5% waste, order 0.42 m³. With an assumed density of 1,600 kg/m³, that is 672 kg = 0.672 metric tonnes, about 0.7408 US short tons.
Frequently Asked Questions
Can I use this for river rock or decorative gravel?
Yes, if you supply a suitable loose bulk density and planned depth for that product. The density scenarios are not verified material specifications.
How does stone size affect coverage?
Larger or irregular stones leave different gaps and can need a different layer thickness for the intended appearance. Volume arithmetic alone cannot choose a suitable size or depth.
Should landscape fabric go under every rock bed?
There is no universal answer in this tool. The choice depends on the planting, soil, water movement and maintenance plan. Fabric area and performance are not calculated.
Can I add two separate beds?
Calculate each bed separately and sum their order quantities, using the same density for the same material. Do not add a second waste percentage to an already allowance-adjusted total.
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