MOT Type 1 Calculator UK - Type 3 & Hardcore Sub-base
MOT Type 1 Calculator (with Type 3 & Hardcore)
Free UK sub-base estimator - tonnes, bulk bags and cost for MOT Type 1, Type 3 and hardcore, with compaction and wastage kept as two separate allowances.
Rectangular area - plan & section
SVG · liveMaterial & allowances
These apply to the area above and drive the weight, purchase and bag estimates.
MOT Type 1 Calculator Results: Volume, Weight, Bags and Purchase Quantity
Bag weights vary by supplier. Check the exact figure they quote before ordering.
Cost estimate
Optional - add your supplier's pricing to estimate a total.
Prices shown in GBP (£) by default - this reflects the price you enter, not a live market rate. Confirm final pricing with your UK aggregate supplier.
Loose load / tipper delivery estimate
Optional - see how many loose loads your order needs.
Vehicle capacities vary by supplier and local access restrictions - treat this as a rough planning estimate.
This free MOT Type 1 calculator UK homeowners, landscapers and groundworkers use to plan a sub-base works as a tonnage calculator, bulk bag calculator and cost estimator in one tool. Pick Rectangular or Circular area using the tabs above, or start from a preset like Path/Patio or Driveway. Enter dimensions in mm, cm, m, in or ft; the diagram and every result update as you type.
How Much MOT Type 1 Do I Need?
To work out how much MOT Type 1 you need, multiply the length and width of the area by your compacted depth to get a volume in cubic metres, then convert that to weight using a density of around 2.1 tonnes per cubic metre. A typical driveway laid at 150mm needs roughly 0.32 tonnes per square metre once compaction and wastage are included, while a garden path at 100mm needs closer to 0.21 tonnes per square metre. The calculator above does this automatically, and separates out the two allowances most other tools blur together - see below.
Type 1 vs Type 3: What's the Difference?
MOT Type 1
A well-graded crushed rock (limestone, granite or similar) with a mix of stone sizes down to dust. The fines lock the larger stones together, which is what makes it compact so hard - ideal as a load-bearing sub-base under driveways, patios and paths.
MOT Type 3
A similar crushed stone but with far less fine material, so it drains freely instead of locking tight. It's specified where water needs to pass through the sub-base, such as under permeable paving or SuDS drainage systems.
Type 3 is specifically required rather than just preferred in a few common situations: under permeable block paving and other SuDS (Sustainable Drainage Systems) installations, and on projects that need to meet the surface water drainage requirements set out in Building Regulations Part H. In these cases, swapping in Type 1 isn't just a minor downgrade - it can mean the finished installation no longer meets the drainage standard it was designed around, since Type 1's fines are exactly what block the free passage of water that Type 3 is chosen for. Despite that, Type 3 rarely gets much space in most guides, which tend to treat it as a footnote to Type 1 - but anyone specifying a permeable driveway, soakaway surround or SuDS scheme needs to get this choice right, not just default to whichever material is more commonly stocked.
Hardcore or recycled 6F2 is a lower grade alternative to Type 1, often made from crushed concrete or brick. It's cheaper and works well as a bulk fill layer, but it's less consistently graded, so many builders add a Type 1 capping layer on top for a smoother finish.
How Deep Should Sub-base Be for a Patio?
For a patio, a compacted sub-base depth of 75-100mm is usually enough - shallower than a driveway needs, because a patio only has to carry foot traffic and garden furniture rather than the weight of a car. Common practice is 75mm on firm, well-drained ground, rising to 100mm on softer or clay-heavy sub-soil where extra stability helps prevent settlement. That's noticeably less than the 150mm (or more) typically specified for a driveway, which has to resist repeated wheel loads and the point-loading from tyres turning on the surface rather than just distributed foot traffic.
A patio sub-base is mainly there to stop the paving from settling unevenly, sinking after rain, or moving as the ground beneath it swells and shrinks with moisture. The Path/Patio preset above already sets the calculator to 100mm as a safe general-purpose default - use the depth field to dial it back to 75mm if your ground is firm and well-prepared, or keep it at 100mm (or slightly more) on softer ground.
Compaction vs Wastage Explained
Almost every sub-base calculator online treats "extra material" as one vague percentage. In practice there are two completely different effects at work, and mixing them up is the main reason people under-order.
- Compaction is a physical property of the material itself. Loose Type 1 straight off the lorry contains a lot of air between the particles. When you run a plate compactor or roller over it, the stones lock together and the layer shrinks in depth - typically by 15-20%, though it can range from 10% on a well-graded, slightly damp material to 30% on a drier or more open-graded stone. If you don't account for this, your finished depth will end up thinner than planned.
- Wastage has nothing to do with the material's physics - it's a buyer's safety margin. It covers spillage during barrowing, an uneven or slightly over-dug sub-grade, material lost around edges and formwork, and general site loss. 10% is a reasonable default for most domestic jobs; tighter, well-prepared sites can use less, and awkward or irregular areas may need more.
Because the two are independent, the calculator applies them as two separate multipliers rather than lumping them into one number - compaction first, to work out the loose volume that will settle down to your target depth, then wastage on top, as a buffer for what actually gets used on site.
How Many Bulk Bags of Type 1 Do I Need?
A standard bulk bag holds around 0.8 tonnes of MOT Type 1, though this varies a little between suppliers, so it's worth checking the bag size they quote before ordering. Once you have your total weight from the calculator, divide it by the bag size and round up, since suppliers won't sell a part-bag. For larger driveways it's often cheaper per tonne to order loose by the load rather than in bulk bags - the loose load estimate above helps you compare.
Worked Examples
| Length × Width × Depth | 3m × 2m × 100mm |
| Compacted volume | 0.60 m³ |
| With 15% compaction + 10% waste | 0.78 m³ |
| Weight at 2.1 t/m³ | ≈ 1.63 t |
| 0.8t bulk bags needed | 3 bags |
| Length × Width × Depth | 6m × 4m × 150mm |
| Compacted volume | 3.60 m³ |
| With 15% compaction + 10% waste | 4.66 m³ |
| Weight at 2.1 t/m³ | ≈ 9.79 t |
| 0.8t bulk bags needed | 13 bags |
Frequently Asked Questions
What is MOT Type 1?
MOT Type 1 is a crushed, well-graded aggregate (commonly limestone or granite) originally specified for road sub-bases by the old Ministry of Transport. It contains a mix of stone sizes from around 40mm down to dust, which allows it to compact into a dense, load-bearing layer under driveways, patios and paths.
What depth of MOT Type 1 do I need?
As a guide, use 100mm for pedestrian paths and patios, 150mm for standard car driveways, and 200mm or more for heavy vehicles, commercial areas or poor ground conditions. Always check any structural or building control requirements for your specific project.
How deep should sub-base be for a patio?
A compacted depth of 75-100mm is typical for a patio - shallower than the 150mm usually needed under a driveway, since a patio only carries foot traffic and furniture rather than vehicle loads. Use the Path/Patio preset above, then fine-tune the depth for your ground conditions.
How do I convert MOT Type 1 volume to tonnes?
Multiply your compacted volume in cubic metres by a density of around 2.1 tonnes per cubic metre, then add allowances for compaction and wastage to reach the weight you should actually order. The calculator above does this conversion automatically from your dimensions.
What's the difference between compaction and wastage allowances?
Compaction accounts for loose material shrinking in depth once it's rolled or plate-compacted, so you need extra volume to reach your target finished depth. Wastage is a separate buffer for spillage, uneven ground and site loss, added after the compaction figure.
Can I use Type 1 instead of Type 3, or the other way round?
They're not always interchangeable. Type 1 compacts tighter and is preferred as a general load-bearing sub-base, while Type 3 has fewer fines and drains more freely, so it's used where water needs to pass through, such as under permeable paving. Check your project's drainage requirements before substituting one for the other.
Can I use MOT Type 1 as a sub base for artificial grass?
MOT Type 3 is usually the better choice for artificial grass rather than Type 1. Type 1 is designed to compact tightly with very little air space, which is great for load-bearing but can trap water underneath the turf; Type 3 has far fewer fines, so it drains more freely and reduces the risk of a soggy or smelly lawn after rain.
Is hardcore the same as MOT Type 1?
No. Hardcore (including recycled 6F2) is typically crushed concrete, brick or similar demolition material, and is less consistently graded than MOT Type 1. It's a cheaper bulk fill option, often topped with a thinner Type 1 capping layer for a more even, compactable surface.
Is a hardcore calculator different from a MOT Type 1 calculator?
Not on this page - this calculator covers both. Switch the material dropdown to "Hardcore / Recycled 6F2" to use the correct density (1.9 t/m³) for hardcore instead of MOT Type 1, and every other setting (compaction, wastage, bulk bags, cost) works the same way.
How many bulk bags of Type 1 equal one tonne?
A standard bulk bag holds around 0.8 tonnes, so roughly 1.25 bulk bags make up one tonne. Bag sizes vary between suppliers, so it's worth confirming the exact weight per bag before working out how many you need.
Do I need to compact MOT Type 1 in layers?
For depths over roughly 150mm, it's generally best to lay and compact the sub-base in stages rather than in one thick layer, so each layer compacts evenly all the way through rather than just at the surface.
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