Construction calculator

Topsoil Quantity Calculator

Coverage area (m²)Compacted depth (m)Compacted density (kg/m³)Waste allowance (%)

Required material mass (kg): -

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Calculation explained

How this result was calculated

The formula, your substituted values, and the evaluated result are shown below.

Formula: area * compactedDepth * density * (1 + wastePercent / 100). Keep every input in the stated units. This result is a quantity-planning estimate; verify site measurements, waste factors, product yields, supplier data, applicable codes, and professional design requirements before construction.

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How the Topsoil Quantity Calculator works

Calculate topsoil quantity for a site works construction scenario using clearly labelled project inputs.

Formula

area * compactedDepth * density * (1 + wastePercent / 100)

Planning guidance

About this calculator

Calculate topsoil quantity for a site works construction scenario using clearly labelled project inputs.

Calculator guide

How the topsoil calculator works

The calculator multiplies the area by the depth you want after settling, then by the soil's density, and adds a waste allowance:

Topsoil (kg) = area (m²) × compacted depth (m) × density (kg/m³) × (1 + waste % ÷ 100)

Divide the result by the density to get cubic metres, which is how most landscape yards sell soil.

Worked example: topsoil for a 50 m² new lawn

Area: 50 m², finished depth 100 mm = 0.1 m
Density of screened topsoil: about 1,300 kg/m³
Allowance for settling and spreading: 15%
50 × 0.1 × 1,300 × 1.15 = 7,475 kg, or about 7.5 tonnes
By volume: 7,475 ÷ 1,300 = 5.75 m³, so order 6 m³

How deep should topsoil be?

Use	Typical topsoil depth
Top-dressing an existing lawn	5–10 mm
New lawn (turf or seed)	75–150 mm
Garden beds	200–300 mm
Vegetable beds	300 mm or more

Why allow for settling?

Loose soil settles as air pockets close and it's watered in, often by 10–20%. That's why the calculator asks for the compacted (finished) depth plus a waste allowance. Allow the higher end for fluffy garden mixes.

Choosing the soil

Ask for a screened soil that meets the Australian standard for soils, landscaping and garden use (AS 4419) if you're buying in Australia. Use a sandy loam for lawns, and an organic-rich garden mix for beds. Test the pH if plants struggle.

Common mistakes

Ordering by the loose depth and ending up short after settling.
Spreading new soil over compacted subsoil without loosening it first, which leads to poor drainage.
Burying existing weeds instead of removing or spraying them first.

How many cubic metres of soil do I need for a lawn?

At 100 mm deep, 0.1 m³ per m² plus about 15%. A 50 m² lawn needs about 5.75 m³.

How much does a cubic metre of topsoil weigh?

Usually about 1.1–1.4 tonnes, depending on moisture and mix.

Can I lay turf straight onto clay?

It's better to spread at least 75–100 mm of sandy loam over loosened clay so the roots can establish and water can drain.

Written by Sam Alex, civil engineer. About the author