Aggregate Calculator

Work out tonnes of aggregate needed for your sub-base, driveway, or path.

Calculate Aggregate Needed

Typical: Patio base 100mm, driveway sub-base 150mm, paths 75mm

Densities used (loose bulk, as of July 2026): MOT Type 1 = 2.0 tonnes/m³, hardcore = 1.9 tonnes/m³, gravel = 1.7 tonnes/m³, sharp sand = 1.6 tonnes/m³. MOT Type 1 and hardcore compact by roughly 20% when whacked down, so the calculator adds a 25% allowance to fill your finished depth (about 2.5 tonnes of MOT Type 1 per compacted m³, in line with supplier coverage charts). Decorative gravel and sharp sand are laid loose, so they get a smaller 5% allowance for spillage and levelling. Aggregates are typically sold in bulk bags (800kg to 1000kg) or loose by the tonne. Always confirm the exact bulk density and bag weight with your supplier.

How This Calculator Works

Aggregate tonnage = Volume (m³) × Density (tonnes/m³) × Compaction factor.

Compacted sub-bases (MOT Type 1, hardcore) use a 25% compaction allowance. Loose materials (decorative gravel, sharp sand) use a 5% spillage allowance instead, because they are not whacked down.

Aggregate Types Explained

  • MOT Type 1: Crushed limestone/granite for sub-bases under driveways, patios, concrete slabs. Compacts well. Most common.
  • Hardcore: Recycled crushed concrete/brick. Cheaper than MOT Type 1, suitable for light-use bases.
  • Gravel: Decorative stone for driveways, paths, borders. Doesn't compact (needs edging).
  • Sharp sand: Bedding layer for block paving, slabs. Not building sand (too fine).

Recommended Depths

ApplicationDepth
Garden path75 mm
Patio base100 mm
Driveway (cars)150 mm
Driveway (heavy vehicles)200 mm+
Sand bedding (paving)30-50 mm

Buying Aggregate

Aggregates sold as:

  • Bulk bags: Typically 800kg-1000kg (around 0.5 m³). Convenient for small projects.
  • Loose tonnes: Delivered loose by lorry. Cheaper per tonne for large projects (3+ tonnes).

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