GardenCalcs.uk
Volume Calculator — Cubic Metres for Garden Projects
Work out volumes for any garden project in cubic metres or litres.
Choose the overall form of the area or container you are filling — a box bed, a round planter, or a pit with sloping sides
Total length of the area or object
Total width of the area or object
Depth or thickness of the material
Extra material to over-order for settling, compaction and spillage — typically 10–15% for loose topsoil, gravel or bark; leave at 0% for a bare-minimum figure
How We Calculate This
Rectangular: Volume = Length × Width × Depth. Cylindrical: Volume = π × Radius² × Depth.
Tapered: uses the prismoidal (pyramidal frustum) formula V = (Depth ÷ 3) × (A_top + A_base + √(A_top × A_base)) to account for sloping sides. The base is taken as 80% of both the top length and the top width.
An optional wastage allowance (default 0%) over-orders the headline volume to cover settling, compaction and spillage — add 10–15% for loose materials like topsoil or bark mulch.
Results are shown in cubic metres, litres (1 m³ = 1,000 L), and the approximate number of bulk bags assuming 0.7 m³ per bag.
Frequently Asked Questions
There are 1,000 litres in one cubic metre. So 0.5 m³ equals 500 litres.
A standard UK bulk bag (also called a tonne bag or dumpy bag) typically holds around 0.6–0.7 cubic metres of loose material, weighing roughly 850kg–1 tonne. This calculator assumes 0.7 m³ per bag. Sizes vary between suppliers — Rolawn standard bags are 0.5 m³ (500 L) and large bags 0.75 m³ (750 L) — so always confirm the bag volume before ordering.
It depends on the material. Topsoil weighs roughly 1.4 tonnes per m³, gravel about 1.8 tonnes per m³, and sand about 1.6 tonnes per m³.
Common depths: mulch 50-75mm, gravel paths 40-50mm, topsoil for lawns 150mm, raised beds 200-300mm.
1 cubic metre = 1,000 litres. So 0.5 m³ = 500 litres. This conversion is useful for ordering compost, soil, and gravel in practical quantities.
Related Calculators
Border Area Calculator
Work out the area of curved or irregular garden borders.
Cost Per Square Metre Calculator
Work out cost per square metre for comparing garden materials.
Material Weight Calculator
Convert between volume and weight for common garden materials.
Area Calculator
Calculate the area of rectangular, circular, and triangular garden spaces.
Slope Calculator
Calculate garden slope gradient, angle, and drainage requirements.
Was this calculator helpful?
One tap. Votes are anonymous and carry the page address, your device type, screen size and country, the numbers in the form and the results on screen, so we can check the answer you saw.
Last updated: February 2026
All calculations are estimates based on standard gardening guidelines. Results may vary with soil conditions, climate, and plant varieties.