Case 1
- Area to cover
- 50m²
- Depth of topsoil
- 10cm
- Bulk density
- 1.33t/m³
6.65t
Open with these valuesTopsoil Calculator
6.65t
Result: 6.65 tArea × depth gives the volume, volume × bulk density gives the weight. 10 m² at 10 cm is 1 m³, and at 1.33 t/m³ that is 1.33 tonnes. Soil is the least predictable material on this site: a sand sits near 1.6 t/m³ and a clay near 1.1, so the same cubic metre swings by half a tonne.
The numbers at a glance
Held fixed: Area to cover 50.00 m², Depth of topsoil 10.0 cm.
| Bulk density (t/m³) | Result (t) |
|---|---|
| 1.20 | 6.00 |
| 1.30 | 6.50 |
| 1.33Your value | 6.65 |
| 1.40 | 7.00 |
| 1.50 | 7.50 |
Worked examples
Case 2
- Area to cover
- 12m²
- Depth of topsoil
- 25cm
- Bulk density
- 1.4t/m³
4.20t
Open with these valuesCase 3
- Area to cover
- 100m²
- Depth of topsoil
- 5cm
- Bulk density
- 1.5t/m³
7.50t
Open with these valuesHow it's calculated
tonnes = area × depth × bulk density
- StepEnter the area in square metres — length × width for a rectangle.
- StepSet the depth: 5–10 cm to dress a lawn, 15–30 cm for a planting bed.
- StepEnter the bulk density; screened topsoil sits between 1.1 and 1.6 t/m³.
- ResultRead the weight, or take the cubic metres from the table and order by volume.
What this number means
Soil density swings more than any aggregate
The source table puts the ideal bulk density of a sandy soil below 1.6 g/cm³ and of a clay below 1.1. That is a difference of half a tonne on the same cubic metre, and moisture moves it further still.
Topsoil is sold both ways
Some suppliers price loose soil by the cubic metre and some by the tonne. The middle column of the table above is the volume for each row, and the density is the only bridge to the weight.
Where the 1.33 t/m³ default comes from
The source states that ideal soil porosity is 50 %, which corresponds to a bulk density of about 1.33 g/cm³. One gram per cubic centimetre is one tonne per cubic metre by definition.
Order for the settled depth
Loose soil consolidates once it is spread, watered and walked on, and a freshly tipped 15 cm layer will not stay at 15 cm. Enter the depth you want afterwards and add 10–20 % for settling.
Commonly misread
The bed needs 1 m³, so I ordered 1 tonne.
Those are different units, and only the bulk density connects them. At 1.33 t/m³ that cubic metre is 1.33 tonnes, a third more than you ordered.
I entered the depth in metres.
Depth is in centimetres here while the area is in square metres. Enter 10 for a 10 cm layer, not 0.1.
Topsoil is topsoil, so the default density will do.
It is an input field because texture and moisture move it between roughly 1.1 and 1.8 t/m³. Over a 10 m³ order that spread is seven tonnes.
Reference table
| Area, depth, density | Volume | Tonnes |
|---|---|---|
| 10, 10, 1.1 | 1 m³ | 1.1 |
| 10, 10, 1.33 | 1 m³ | 1.33 |
| 10, 10, 1.6 | 1 m³ | 1.6 |
| 13.3, 5, 1.5 | 0.665 m³ | 1 |
| 20, 15, 1.33 | 3 m³ | 3.99 |
Questions
How much topsoil do I need?
Multiply the area by the depth of the layer, then by the bulk density. For 10 m² at 10 cm the volume is 1 m³, and at 1.33 t/m³ that is 1.33 tonnes.
How deep should topsoil be?
It depends on what grows in it. Dressing an existing lawn takes 5 to 10 cm, a new lawn 10 to 15 cm, and a planting bed or vegetable plot 20 to 30 cm. Deeper beds hold more water and let roots down further.
What bulk density should I enter?
About 1.33 t/m³ is a good middle figure and is the default here. The source table gives ideal values below 1.6 for sandy soils, below 1.4 for loams and below 1.1 for clays, and wet soil weighs more than any of them.
How many square metres does a tonne of topsoil cover?
At 1.5 t/m³ one tonne is 0.67 m³, which covers about 13 m² at 5 cm or 6.7 m² at 10 cm. Divide 1 by the density and by the depth in metres for any other combination.
Should I order a little extra?
Yes. Loose soil consolidates once it is spread and watered, so a layer laid at the depth you entered ends up thinner. Around 10–20 % more is sensible, more again on an uneven site.
Sources and last check
Information, not professional advice.