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Aggregate and MOT Type 1 Calculator

How Much MOT Type 1 Do I Need? Calculate Volume and Tonnes for Driveways, Car Parks and Paths

Sub-base is sold by the tonne but designed by depth. Learn how to turn length, width and compacted depth into m³ and tonnes, how compaction and wastage change the order, and what depth of Type 1 a driveway needs, with worked examples and a free calculator.

Last updated 7 November 2026

Why the order quantity is not just length × width × depth

Sub-base is designed as a finished, compacted thickness, but it arrives as loose material and is sold by weight. To order the right amount you need to turn depth into volume, allow for compaction and waste, and convert to tonnes. Order too little and the job stops while you wait for another load. Order too much and you pay for material and its removal.

KaelSite’s free Aggregate and MOT Type 1 Calculator does the whole chain for driveways, road sub-bases, car parks, footpaths and construction platforms.

What is MOT Type 1?

MOT Type 1 is a crushed, graded, unbound granular sub-base material widely used under driveways, roads, car parks and paving. It compacts to a dense, stable layer that spreads loads to the ground below. Related materials include:

  • Type 2: a similar granular sub-base with a different grading.
  • Type 3: an open-graded material often used where drainage is needed.
  • Scalpings, crushed concrete and ballast: used as fill or sub-base depending on the specification.

The calculation step by step

Work in metres.

  1. Compacted volume = length × width × compacted depth
  2. Add compaction allowance: compacted volume × (1 + compaction %)
  3. Add wastage: that result × (1 + wastage %)
  4. Tonnes = order volume × bulk density

The calculator applies compaction and wastage one after the other. A common guide density for compacted Type 1 is about 2.1 t/m³, but quarries quote different densities for loose and compacted material, so use the figure on your delivery ticket or specification.

Worked examples

The allowances below are examples only. Use the figures from your design or supplier.

1. Driveway
12 m × 4 m with 150 mm of compacted Type 1:
12 × 4 × 0.15 = 7.2 m³
With 20% compaction: 7.2 × 1.20 = 8.64 m³
With 5% wastage: 8.64 × 1.05 = 9.07 m³
At 2.1 t/m³: 9.07 × 2.1 = about 19 tonnes
As an example only, at £25 per tonne the material would cost about £476.

2. Car park
30 m × 20 m with 200 mm compacted depth:
30 × 20 × 0.2 = 120 m³
With 15% compaction and 5% wastage: 120 × 1.15 × 1.05 = 144.9 m³
At 2.1 t/m³: about 304 tonnes

3. Footpath
20 m × 1.2 m with 100 mm compacted depth:
20 × 1.2 × 0.1 = 2.4 m³
With 10% compaction and 5% wastage: 2.4 × 1.10 × 1.05 = 2.77 m³
At 2.1 t/m³: about 5.8 tonnes

What depth do I need?

The right depth depends on the ground, the expected loads and the finished surface. Many private driveways use roughly 100 to 200 mm of compacted Type 1 under the wearing course, and the calculator suggests 150 mm as a starting point. Car parks, roads and platforms usually need more. Always follow the design or supplier guidance, and remember that soft or variable ground may need extra depth or a geotextile layer.

Compaction versus wastage

These are different allowances:

  • Compaction covers the extra loose material needed to reach the finished thickness after rolling or plating.
  • Wastage covers spill, overbreak and handling losses on site.

Both increase the order, so enter each separately rather than guessing one combined figure.

Common mistakes

  • Using loose depth instead of compacted depth. The design depth is the finished thickness.
  • Using the wrong density. Check the ticket or specification rather than a generic number.
  • Forgetting the allowances. Without compaction and wastage you will usually run short.
  • Mixing units. Entering depth in millimetres as if it were metres gives a result 1,000 times too large.
  • Ignoring the shape. Curves, tapers and cut-outs mean the area is not a simple rectangle. Split it into sections.
  • Compacting in one thick layer. Material is normally laid and compacted in layers to reach proper density.

UK points to know

The grading and properties of Type 1 are defined in the Specification for Highway Works, and suppliers normally sell material that meets it. For domestic jobs, check the rules on hard surfacing in front gardens. In England, paving over more than 5 square metres with a non-porous surface may need planning permission unless it is permeable or drains to a lawn or border. Permeable surfaces often use different sub-base materials and depths, so confirm the specification before you order.

Frequently asked questions

How do I calculate MOT Type 1 quantity?
Multiply length by width by compacted depth in metres, add compaction and wastage, then multiply by the bulk density to get tonnes.

What depth of Type 1 do I need for a driveway?
Commonly 100 to 200 mm compacted, depending on the ground and the finished surface. Follow your design or supplier advice.

What density should I use?
About 2.1 tonnes per cubic metre is a common guide figure. Use the density on your delivery ticket where you can.

What is the difference between compaction and wastage allowance?
Compaction is the extra loose material needed to reach the compacted depth. Wastage is spill and site loss. They are applied one after the other.

How do I convert aggregate volume to tonnes?
Multiply the volume in m³ by the bulk density in t/m³. For example, 10 m³ at 2.1 t/m³ is 21 tonnes.

Can I use it for scalpings or crushed concrete?
Yes. Pick the material or enter a custom density, as the volume maths is the same.

Related calculators

Sub-base sits between the dig and the surface. These tools cover the steps around it:

See all of them in our complete guide to free construction calculators.

Keep your groundworks records in one place

Sub-base checks, compaction records and photos all need recording as the work goes in. KaelSite helps UK site teams manage inspections, safety and reporting from one mobile-first app. Explore KaelSite features.

References