Topsoil & Mulch Calculator — m, m³, bags
How to use this calculator
Pick the bed shape — rectangle, circle, L-shape, or a known area in m² — and enter dimensions in metres, centimetres, or millimetres. Choose the material, set spread depth, and add a waste allowance for uneven subgrade and settling. Loose-delivered material is sold by the cubic metre; bagged products come in 25 L, 40 L, or 50 L sacks (1 m³ = 1 000 L).
Depth drives quantity far more than footprint: doubling depth doubles volume. Spread bark or wood mulch 5–8 cm for beds and up to 15 cm for weed suppression; lay screened topsoil 10–15 cm for new turf and 20–30 cm for raised garden beds. Bulk topsoil is loose-measured, so order roughly 10–15% over the geometric volume. To excavate an existing bed first, size the dig with the excavation volume calculator and balance haul-off against import using cut and fill.
Saved Calculations
| Time | Shape | Material | Area m² | Vol m³ | Bags | Weight | Cost |
|---|
How to Calculate Topsoil & Mulch (Metric)
Soil and mulch are sold loose-measured by the cubic metre, so the workflow is: measure the bed footprint, decide a finished spread depth, convert to m³, then pad for spreading loss and settling. The waste slider defaults to 5% for flat, clean ground and should be raised to 10–15% for sloped or irregular beds where material over-spreads at the edges. Bag counts round up — partial bags are never sold.
Formulas
Volume (m³) = Area (m²) × Depth (m). Rectangle Area = L × W; Circle Area = π × (D ÷ 2)²; L-shape = (A × B) − (C × D). Bags = ⌈Volume in litres ÷ bag litres⌉, where m³ × 1 000 = litres. Weight = Volume × density (kg/m³). Truck loads = m³ ÷ 10. A waste factor w is applied as Volume × (1 + w).
Material Densities
Densities are loose, as-delivered approximations and vary with moisture: topsoil ≈ 1 200 kg/m³ (≈ 1.2 t) · garden soil ≈ 1 070 · compost ≈ 600 · wood-chip mulch ≈ 360 · bark mulch ≈ 300 · rubber mulch ≈ 710 · peat moss ≈ 240 · fill sand ≈ 1 600 kg/m³. Wet topsoil can weigh 20–30% more, which matters for delivery vehicle capacity.
FAQ
How deep should I apply mulch? 5–8 cm for flower beds, 8–10 cm for pathways, up to 15 cm for weed suppression. How deep for topsoil? 10–15 cm for new lawns, 20–30 cm for garden beds. Bulk or bags? Above roughly 1.5 m³, loose bulk delivery is usually cheaper per cubic metre than bags despite delivery fees. Why is delivered volume more than I calculated? Bulk soil is sold loose and swells 20–30% over compacted bank volume, so always keep the waste allowance. For aggregate base under a path use the gravel & aggregate calculator; for backfilling around new work see the fill & backfill calculator, and for footing soil to be reinstated see the concrete pier calculator.
Ordering tips
In 2025 Europe, bagged bark or wood mulch typically runs €4–8 per 50 L sack at garden centres; loose bulk mulch is €30–60 per m³ delivered. Screened topsoil is €25–55 per m³ delivered, BS 3882-grade quality blend €40–80 per m³. The most common over-order mistake is forgetting that loose-measured bulk soil settles: 10 cm of fresh topsoil shrinks to roughly 8 cm after one good rain, so order with the compacted-depth checkbox on for new lawns and driveway bases. Delivery typically costs €40–90 inside a 15 km radius; combining drops saves a haulage charge. Aged hardwood mulch holds colour longer than fresh chips and is preferred for visible front-yard beds. Raised vegetable beds need a graded organic blend (BS 3882 or equivalent), not pure bulk topsoil — pure mineral soil compacts too hard for roots.
