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Mulch / Soil / Gravel Coverage Calculator

Whether you are filling a garden bed, refreshing a mulch layer, or laying gravel on a driveway, the first question is how much material to buy. Enter the area (length × width) and target depth to get the volume needed in litres, cubic metres and cubic yards. The tool also rounds up the bag count to the next whole bag and multiplies by your unit price to give a budget ceiling.

Common depths
Common bag sizes

Volume needed

3.00 ≈ 3,000 L · 3.92 yd³

Bags (rounded up)

60

Estimated total

300

Area = length × width. For irregular beds, convert to the equivalent rectangle first; bag volume in litres is usually printed on the side of the bag.

Formula

Area (m²) = length (m) × width (m) Volume (m³) = area × (depth cm ÷ 100) Volume (L) = volume (m³) × 1000 Volume (yd³) = volume (m³) × 1.30795 Bags = ⌈volume (L) ÷ bag size (L)⌉ Total cost = bags × price per bag

Frequently asked

My garden bed is not a rectangle — how do I work out the area?

Break the shape into smaller rectangles / triangles, work out each piece, then enter the total as any "length × width" combination that gives the same product (e.g. enter 4 m × 3 m for a 12 m² total). For a circular bed, area = π × radius²; for irregular curves, measure the widest and longest spans and multiply by 0.79 (≈ π/4) as a circle correction. Even with rough shapes the error is usually within ±10 %, which is fine for deciding how many bags to buy.

My bag is labelled in cubic feet or kilograms, not litres — how do I convert?

Volume conversions: 1 ft³ = 28.32 L and 1 yd³ = 764.55 L, so a typical US 2 ft³ mulch bag ≈ 56.6 L and a 3 ft³ bark bag ≈ 84.9 L. If only the mass is printed (e.g. 25 kg topsoil), divide by the loose bulk density to get volume: topsoil and mulch ≈ 700–800 kg/m³, gravel ≈ 1,500–1,700 kg/m³. So 25 kg of topsoil ≈ 25 / 0.75 ≈ 33 L and 25 kg of gravel ≈ 25 / 1.6 ≈ 15 L. The most reliable number is the "yield" or "covers" figure printed on the bag itself.

Should I buy bags or bulk loose material?

For small DIY jobs (< 1 m³, e.g. one or two beds), bagged material is easiest — light to carry, easy to store, and you can stop part-way. Above 1–2 m³, bulk (dump truck or 1 m³ bulk bag) is typically 30–50 % cheaper per m³, but you need to account for delivery fees, somewhere to drop the pile, and the fact that leftover loose material dries out or washes away. A useful threshold: once you cross ~30 bags (≈ 1.5 m³), it is worth asking the supplier for a bulk quote. Under ~10–15 bags, bagged usually wins.

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