MOT Type 1 Aggregate Calculator
Use this sub-base calculator to estimate how much MOT Type 1 stone you need for a driveway, patio, path, or foundation layer.
Tip: For domestic driveways, a sub-base depth of 100-200mm is common depending on ground conditions and expected traffic.
What Is MOT Type 1?
MOT Type 1 is a crushed aggregate commonly used as a sub-base in UK construction and landscaping. It contains a mix of stone sizes, from larger pieces down to fine dust, which helps it compact tightly and create a strong, stable layer. You will often see it used under driveways, patios, paths, and roads before the final surface is installed.
Because it forms the structural base, ordering the right amount is important. Too little material can lead to weak areas, settlement, and expensive rework. Too much can create unnecessary cost, waste, and extra handling.
How This MOT Type 1 Calculator Works
This calculator estimates material in a practical way by combining geometry and real-world ordering assumptions:
- Area: length × width
- Compacted volume: area × depth (converted from mm to m)
- Loose order volume: compacted volume × compaction factor
- Total with wastage: loose volume × (1 + wastage %)
- Tonnage: total volume × bulk density
It also estimates bag quantities so you can quickly compare loose loads versus bulk bags.
Typical Depth Guide for Sub-Base
Pedestrian paths
Usually around 75mm to 100mm compacted depth, depending on soil strength and drainage.
Patios and garden seating areas
Typically 100mm to 150mm compacted sub-base under paving.
Domestic driveways
Often 150mm to 200mm compacted depth, especially where cars are parked regularly.
Heavier vehicle use
May require deeper build-ups and engineered specification. If in doubt, consult a structural engineer or experienced groundworker.
Why Compaction and Density Matter
Many people calculate volume and stop there, but aggregate is usually delivered loose and then compacted in layers. That means you often need more loose stone than the final compacted volume suggests. A compaction factor helps account for this difference.
Density also matters when converting volume to tonnes. Different quarries can vary slightly, so always check supplier data when possible. The default value in this calculator (2.2 t/m³) is a common planning assumption for MOT Type 1.
Example Calculation
Imagine a driveway that is 10m long and 4m wide with a compacted sub-base depth of 150mm:
- Area = 10 × 4 = 40 m²
- Compacted volume = 40 × 0.15 = 6.00 m³
- Loose volume (factor 1.25) = 7.50 m³
- With 10% wastage = 8.25 m³
- Tonnage (2.2 t/m³) = 18.15 tonnes
So a practical order would likely be around 18 to 19 tonnes, depending on delivery increments and site tolerance.
Practical Ordering Tips
- Round up, not down, especially on irregular sites.
- Add extra allowance for poor ground or soft spots.
- Compact in layers (often 50mm-75mm passes) for best performance.
- Confirm whether your supplier sells by tonne, cubic metre, or bag.
- Check access width, turning space, and unloading position before delivery day.
Related Tools and Keywords You Might Need
If you are planning groundwork, you may also find these search terms useful: sub-base aggregate calculator, hardcore calculator, driveway stone calculator, tonnes to cubic metres aggregate, and MOT Type 1 coverage per tonne.
Final Thoughts
A reliable MOT Type 1 estimate can save both money and time on your project. Use the calculator as a strong starting point, then confirm final quantities with your installer or supplier based on real site conditions. Good preparation at sub-base stage leads to a better, longer-lasting finish above.