Question 1

How much does soil swell when you dig it up?

Accepted Answer

Dug soil expands (bulks) because it loses its natural compaction. Topsoil and clay typically swell by around 25%, sandy soil by around 12%, and broken rock or hardcore by up to 50%. Enter your dimensions and material type above to see your exact loose volume.

Question 2

How many tonnes is 1m³ of topsoil or clay?

Accepted Answer

Screened topsoil is around 1.5 tonnes per m³ in the ground. Subsoil and clay are heavier, typically 1.8–2.0 tonnes per m³, especially when wet. Select your material above to use the correct density automatically.

Question 3

How do I work out how many dump trailer loads I need?

Accepted Answer

Divide your loose (bulked) volume by your trailer’s volume capacity in m³, and separately divide your total weight by your trailer’s tonnage limit — whichever number is higher is your real load count, since trailers are limited by both space and legal payload. This calculator does both automatically for common trailer and grab lorry sizes.

Question 4

How much spoil comes out of a slurry lagoon or tank dig?

Accepted Answer

Use the length, width and depth of the planned excavation (or diameter and depth for a circular lagoon) to get your in-ground volume, then select your ground material to see the tonnage and loose volume once dug. This is worth checking before ordering trailers or booking a digger, since clay-heavy sites can produce far more loose spoil than the hole itself suggests.

Question 5

What is the capacity of an 8-wheel grab lorry?

Accepted Answer

A standard UK 8-wheel grab lorry has a legal payload of around 16 tonnes, which typically equates to 12–14m³ of loose spoil depending on material density. Heavier materials like wet clay or stone will hit the weight limit before the load bed is full.

Question 6

Do I need to remove topsoil separately from subsoil?

Accepted Answer

For most groundworks, yes — topsoil is often kept on-site for reinstatement or landscaping, while subsoil and clay are usually the material that needs removing or is used for bunding. Run this calculator once for each layer if your dig has more than one material type.

Material	Density t/m³	Swell %	Notes
Topsoil (screened)	1.5	25%	Standard screened topsoil
Subsoil / Clay	1.8	25%	Heavier — common below topsoil
Wet / Sticky Clay	2	30%	Saturated clay — swells more, heavier
Sandy / Loamy Soil	1.6	12%	Lighter, swells less than clay
Hardcore / Stone	2.2	50%	Rubble, stone, broken concrete

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