Aggregates & Sub Base Calculator
Work out the tonnes, bulk bags or 25 kg bags of aggregate you need, Type 1, ballast, sand, gravel, topsoil and more.
Densities are nominal UK averages and change with moisture, source and compaction. Sub base is quoted at compacted density. Bulk (“tonne”) bags typically hold about 0.5 m³ (roughly 800 kg of ballast). Order a little extra for compaction and levelling.
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How to use the aggregate calculator
Enter the area in square metres and the depth in millimetres, choose your material, and the calculator returns the volume, the weight in tonnes and the number of bulk bags you need. It uses typical UK yard densities, for example MOT Type 1 at around 2.1 tonnes per cubic metre.
For a compacted sub base such as Type 1, add a 5, 10% allowance so you order enough to compact down to depth. Densities vary with moisture and quarry source, so round up when ordering.
Frequently asked questions
How many tonnes of MOT Type 1 do I need?
Multiply the area (m²) by the depth (m) for the volume in cubic metres, then multiply by 2.1. For example, 20 m² at 100 mm is 2 m³, about 4.2 tonnes.
How many bulk bags are in a tonne?
A standard bulk (dumpy) bag holds roughly 800 kg of aggregate, so one tonne is about 1.25 bulk bags.
What is the density of MOT Type 1?
MOT Type 1 has a typical compacted density of around 2.1 tonnes per cubic metre; it varies with moisture and quarry source.
How do I calculate how much aggregate I need?
Volume (m³) = area (m²) × depth (m), then tonnes = volume × the material’s density.