Aggregates Calculator UK

Standard sub-base for driveways, paths, patios.
DIMENSIONS
Typical depths:
Ready to Calculate
Enter your dimensions and material choice to see the estimated quantity and cost.

How to use this Aggregates Calculator

  1. Select your material: Choose from MOT Type 1, Ballast, Sharp Sand, Gravel, and more.
  2. Choose your shape: Select Rectangle. For complex gardens, use the “Irregular” tool to add multiple areas together.
  3. Enter dimensions: Use the toggle at the top to switch between Metric (metres) and Imperial (feet).
  4. Set the depth: Enter your depth in mm (or inches). Use the quick buttons for standard depths like Driveways (50mm) or Patios (75mm).
  5. Check results: Instantly see the Area (m²), Volume (m³), and Weight (Tonnes) required.

How we calculate volume and tonnes

The core formula for calculating aggregate is simple geometry multiplied by density:

Area (m²) × Depth (m) = Volume (m³)
Volume (m³) × Density (tonnes/m³) = Weight (tonnes)

For example, a driveway that is 10m long, 5m wide, and 50mm (0.05m) deep:
10 × 5 = 50 m² (Area)
50 × 0.05 = 2.5 m³ (Volume)
If using MOT Type 1 (density ~2.2):
2.5 × 2.2 = 5.5 Tonnes required.

Choosing the right aggregate

Sub-bases (MOT Type 1)

The essential load-bearing layer for driveways and patios. It compacts to form a solid surface that prevents sinking. Type 3 is used where drainage is a priority.

Decorative Gravels

20mm Gravel: Best for driveways as it doesn’t get stuck in tyre treads.
10mm / Pea Shingle: Better for garden paths and pipe bedding.

Building Sands

Sharp Sand: Gritty, used for screeds and laying block paving.
Soft/Building Sand: Smooth, used for bricklaying and pointing.

Ballast

A mixture of sand and small stones (20mm). This is the standard mix used to make concrete for foundations and fence posts.

Frequently Asked Questions

MOT Type 1 is a granular sub-base material approved by the Ministry of Transport. It consists of crushed stone ranging from 40mm down to dust. This size range allows it to compact extremely tightly, creating a solid, stable load-bearing layer for driveways, patios, and roads.
To convert cubic metres (m³) to tonnes, you multiply the volume by the bulk density of the material. For example, if you have 1 m³ of Limestone (density approx 2.2), the calculation is 1 × 2.2 = 2.2 tonnes.
A standard 'bulk bag' (or jumbo bag) typically contains roughly 850kg of material, though some are 800kg or 1000kg. Our calculator assumes a standard 850kg bag. If you need 1.7 tonnes, that would be exactly 2 bulk bags (1.7 tonnes = 1700kg / 850kg = 2).
For a driveway, we recommend a finish depth of 50mm–60mm using 20mm gravel. If you go deeper (e.g., 100mm), cars will sink into it and struggle to gain traction. If too shallow, the sub-base may show through.
Yes. When you vibrate or roll a sub-base (like MOT Type 1), it loses volume as air gaps are removed. We recommend allowing 20% extra volume for compaction on sub-bases. For wastage (spillage, cuts), a standard 10% allowance is safe.
The weight of aggregate varies significantly depending on moisture content (wet sand is much heavier than dry sand) and the specific type of rock. Our calculator uses industry-standard averages, but exact weights can vary by batch.
You can toggle between Metric (metres, millimetres) and Imperial (feet, inches) at the top of the calculator. The results will always provide the UK standard outputs in Tonnes and Metres.

Disclaimer: Densities used are industry averages. Moisture content and specific rock types can vary the weight significantly. Always order slightly more than calculated to account for compaction and ground unevenness.