Methodology & Sources
How the calculator turns dimensions into planning estimates.
Last reviewed: 3 September 2026
Volume formulas
All dimensions are converted to metres. Depth entered in millimetres is divided by 1,000 before it is used.
- Rectangle: length × width × depth.
- Circle: π × radius² × depth.
- Triangle: ½ × base × height × depth.
The resulting cubic metres are the primary result. The calculator does not add a hidden waste, settlement or compaction allowance.
Indicative weight coefficients
Estimated tonnes equal cubic metres multiplied by the selected coefficient. These are planning defaults, not certified measurements of a product:
- Mulch: sugar cane 0.20; pine bark 0.30; bark 0.35; wood chip and eucalyptus 0.40; cypress 0.45; hardwood 0.50 tonnes per cubic metre.
- Soil: potting mix 0.60; veggie mix 0.90; garden mix 1.00; topsoil 1.10; turf underlay 1.20; sandy loam 1.30; clay soil 1.50 tonnes per cubic metre.
- Gravel: crushed granite, crushed sandstone and recycled aggregate 1.40; blue metal, limestone and decorative pebbles 1.50; river pebbles 1.60 tonnes per cubic metre.
- Sand: most listed sands 1.50; paving sand 1.60 tonnes per cubic metre.
- Road base: recycled road base and crusher dust 1.60; FCR 1.70; DGB10, DGB20 and quarry rubble 1.80 tonnes per cubic metre.
As an Australian supplier cross-check, Australian Native Landscapes publishes indicative loose values including 0.3 tonnes per cubic metre for bark, 0.4 for woodchip, 1.2 for garden mix, 1.4 for topsoil, 1.3–1.5 for its listed sands, 1.45 for blue metal and 1.75 for road base. Its table also warns that grade, mineral content, moisture and source change density. See ANL's landscape product weights and volumes.
LandscapeCalc intentionally exposes its coefficients because a local supplier's conversion should replace a default whenever it is available. A difference between this calculator and a supplier is not an ordering tolerance: use the supplier's figure for that product.
Ordering equivalents and rounding
The mulch calculator also shows litres: cubic metres × 1,000. A litre is one cubic decimetre, as defined in the BIPM SI Brochure (checked 20 October 2026). If you enter a bag size in litres, the calculator divides the unrounded total litres by that size and rounds up to whole bags. The bag size comes from your product label; no retail pack size is assumed.
The 20 kg equivalent divides estimated weight in kilograms by 20 and rounds up to a whole unit. It is a mass comparison only; landscape products may instead be sold loose, by volume or in bags measured in litres.
The 1 m³ bulk-bag equivalent divides volume by one cubic metre and rounds up. Suppliers offer different bulk-bag sizes and weight limits, so this is not a retail pack count.
Cubic metres and tonnes are displayed to two decimal places; litres use up to two decimal places. The unrounded values are used before whole-unit equivalents are rounded up, with floating-point noise normalised at whole-bag boundaries.
Depth and project requirements
The depth buttons are editable starting points, not design advice. Required depth can depend on the product, intended use, subgrade, drainage, compaction and project specification. Enter the depth provided by the relevant supplier, designer, installer or approved project documentation.
Known limitations
- Natural and recycled products vary between sources and batches.
- Moisture and compaction can materially change weight and delivered volume.
- The calculator does not determine product suitability, structural requirements, transport capacity or legal load limits.
- Bulk deliveries and bags should be ordered using the supplier's current specification and sale unit.
If a formula, coefficient or source needs correction, please use the Contact page.