Aggregate Calculator (UK)
Last updated: 12 August 2026
Work out how much MOT Type 1, gravel, sand or topsoil you need. Enter your area and depth and get the answer in cubic metres, tonnes and bulk bags.
How the calculation works
Volume = length × width × depth (converted to metres). We multiply the volume by the material bulk density to get tonnes, then divide by 850kg for the number of bulk bags. Densities vary with moisture and compaction, so treat the result as a close estimate and round up when ordering.
Typical depths
Patios and paths: 100mm compacted MOT Type 1 sub-base. Driveways: 150mm or more, compacted in layers. Decorative gravel: 40–50mm. Turf topsoil: 100–150mm.
Aggregate densities and coverage
| Material | Density | Bulk bag covers |
|---|---|---|
| MOT Type 1 | 2.1–2.3 t/m³ | ~8 m² at 50mm |
| Gravel / shingle | 1.6 t/m³ | ~10–12 m² at 40–50mm |
| Sharp sand | 1.7 t/m³ | ~10 m² at 50mm |
| Topsoil | 1.5–1.6 t/m³ | ~5 m² at 100mm |
Frequently asked questions
How much does a bulk bag of aggregate cover?
A typical bulk bag holds around 850kg. One bulk bag of MOT Type 1 covers roughly 8 square metres at 50mm deep, and one bulk bag of decorative gravel covers about 10 to 12 square metres at 40 to 50mm.
How many bulk bags of MOT Type 1 do I need for 10 square metres?
At 100mm deep, 10 square metres needs 1 cubic metre, which is about 2.2 tonnes of MOT Type 1 — roughly three 850kg bulk bags.
How deep should MOT Type 1 sub-base be?
For patios and paths, 100mm of compacted MOT Type 1 is typical. Driveways usually need 150mm or more, compacted in layers. Add the depth of your surface material on top.
How many tonnes is a cubic metre of gravel?
Loose gravel and shingle weigh roughly 1.6 tonnes per cubic metre. MOT Type 1 is denser at around 2.1 to 2.3 tonnes per cubic metre once compacted, and sharp sand is about 1.7 tonnes per cubic metre.
What is MOT Type 1?
MOT Type 1 is a crushed stone sub-base material graded from 40mm down to dust, named after the old Ministry of Transport specification. It compacts into a firm, stable layer under driveways, patios and paths.
Related calculators
Gravel Calculator
Gravel, shingle and chippings in tonnes and bulk bags.
Block Paving Calculator
Paving blocks, sub-base and sand for a driveway or patio.
Topsoil Calculator
Topsoil in m³, tonnes and bulk bags for lawns and beds.
Estimates are for guidance only. Material dimensions, densities and coverage vary by supplier — always confirm quantities before ordering, and consult a qualified professional for structural work.