How many litres in a cubic metre?

There are 1,000 litres in one cubic metre. So 0.5 m³ equals 500 litres.

How big is a bulk bag?

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.

How do I convert cubic metres to tonnes?

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.

What depth should I use for garden projects?

Common depths: mulch 50-75mm, gravel paths 40-50mm, topsoil for lawns 150mm, raised beds 200-300mm.

How do I convert cubic metres to litres?

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.

GardenCalcs

Volume Calculator — Cubic Metres for Garden Projects

Work out volumes for any garden project in cubic metres or litres.

ShapeChoose the overall form of the area or container you are filling — a box bed, a round planter, or a pit with sloping sides

Length

Total length of the area or object

Width

Total width of the area or object

Depth

Depth or thickness of the material

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

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Last updated: February 2026

All calculations are estimates based on standard gardening guidelines. Results may vary with soil conditions, climate, and plant varieties.