MOT Type 1 Sub-Base: How Much Do I Need? (Calculator + Guide)
MOT Type 1 is the crushed stone sub-base that sits under most patios, paths, shed bases and driveways. Get the quantity wrong and you either run short halfway through compacting or end up with a bag left on the drive. This guide explains what MOT Type 1 is, the depths commonly used for each job and how to turn your measurements into tonnes and bulk bags. If you just want the answer, our free aggregates calculator does the sum for you.
Quick answer: length × width × compacted depth (in metres) gives the finished volume. Add 20 to 30% for compaction and waste, multiply by about 1.7 tonnes per m³ for loose MOT Type 1, then divide by 0.8 for 800kg bulk bags and round up. Use the aggregates calculator to do it in seconds.
Use the aggregates calculator
Our aggregates calculator works out MOT Type 1, hardcore, sharp sand, building sand, gravel and all-in ballast. You can:
- Pick a job to start from a typical depth: patio sub-base (100mm), path sub-base (75mm), shed base sub-base (100mm), driveway sub-base (150mm), sharp sand bedding layer (40mm), gravel top layer (40mm) or something else. You can change any of the settings.
- Enter the length, width and finished depth after compaction, and an allowance for compaction, settling and waste (20 to 30% is typical for a compacted sub-base).
- See the volume, the weight in tonnes and the number of bags (800kg bulk bags, or 25kg bags where we sell them), priced live from the shop, and add them straight to your basket.
It is an estimate. Ground, compaction and moisture vary, so allow for your own site conditions.
What is MOT Type 1?
MOT Type 1 is crushed stone graded from about 40mm down to fine dust. The fines fill the gaps between the larger pieces, so when it is compacted with a plate compactor it locks together into a firm, stable layer that spreads the load from whatever sits on top. We sell it as an MOT Type 1 sub-base bulk bag (800kg). If you are weighing it up against other stone, see our guide to MOT Type 1 vs Type 3.
Typical uses and compacted depths
The right depth depends on the ground and what is going on top. The figures below are the typical starting points the calculator uses, not a specification. Always follow your paving, slab or driveway manufacturer's guidance, or ask your installer.
| Job | Typical compacted depth | More detail |
|---|---|---|
| Garden path | 75mm | Path and shed base guide |
| Patio | 100mm | Patio guide |
| Shed base | 100mm | Path and shed base guide |
| Driveway | 150mm | Driveway sub-base guide |
Soft or clay ground, heavier loads or vehicle use generally call for more depth. Our guide on how deep a patio sub-base should be goes into this in more detail.
How to work out volume and tonnes
- Area. Length × width in metres. Split L-shapes and irregular areas into rectangles and add them together.
- Finished volume. Area × compacted depth in metres (100mm = 0.1m).
- Allowance. Loose stone packs down when compacted, and some is lost to settling and uneven ground. Add 20 to 30%; 25% is a sensible middle figure.
- Tonnes. Multiply by the loose density. The calculator uses about 1.7 tonnes per m³ for loose MOT Type 1, hardcore and all-in ballast, and about 1.6 tonnes per m³ for sands and gravel. With a 25% allowance, MOT Type 1 works out at roughly 2.1 tonnes per m³ of finished, compacted sub-base.
- Bags. Divide the tonnes by 0.8 for 800kg bulk bags and round up.
Worked example
A 4m × 3m patio at 100mm deep is 12m² × 0.1m = 1.2m³ finished. With a 25% allowance that is 1.5m³ to order. 1.5 × 1.7 = about 2.55 tonnes of MOT Type 1, so four 800kg bulk bags. These figures are typical; moisture and the quarry make a difference. For more on converting between tonnes, cubic metres and bags, see tonnes vs bulk bags.
Compaction tips
- Dig to the full depth. Allow for the sub-base, any bedding layer and the paving itself, plus a fall for drainage where needed.
- Remove topsoil and roots and firm up the exposed ground before laying any stone.
- Build up in layers. Spread, rake level and compact with a plate compactor. For thicker bases, lay and compact in more than one layer. Follow the hire company's guidance for the machine.
- Keep it damp, not soaking. Slightly moist stone generally compacts better than bone-dry material.
- Check the level as you go so you are not making up the difference with bedding material later.
Bulk bag vs loose
Aggregates are usually supplied either in bulk bags or as a loose load tipped from a lorry. Bulk bags keep the stone contained and tidy and are easy to count against your calculation; a loose tipped load needs space to drop it and may need covering or clearing up afterwards. We supply MOT Type 1 in bulk bags of approximately 800kg (the packed weight can vary a little with moisture). They are delivered by lorry with a truck-mounted forklift and offloaded at your site, so you need a firm, level place with suitable access, and someone must be there to receive the delivery. Think about how far you will then barrow the stone.
Need only a small top-up? Call us on 03330 908479.
Ordering and delivery
Browse MOT Type 1, sands, gravels and cement at trade prices in our aggregates and cement collection. Prices are shown excluding VAT.
- Minimum order: £250 ex VAT for timber, aggregates and cement (all counted together).
- Delivery: £25 ex VAT on orders under £500 ex VAT, free from £500 ex VAT.
- Where: we deliver to addresses in England only.
See our delivery information for full details, or call 03330 908479 and we will happily check your quantities before you order.
Frequently asked questions
How many tonnes of MOT Type 1 per m²?
At 100mm compacted depth with a 25% allowance, very roughly 0.21 tonnes per m². Treat it as a guide only and use the calculator for your own dimensions.
Why add an allowance?
MOT Type 1 is delivered loose with air between the pieces. Compacting it packs it down, so you need more loose material than the finished depth suggests.
Can I work out sand and gravel too?
Yes. Work out each material separately in the calculator and add them to your basket one at a time; the minimum order counts all your aggregates and cement together. For bedding under slabs see sand and cement for paving.
The quantities in this guide are estimates. Ground levels, the depth you dig, how well the material is compacted and how wet it is all change what you need, and densities vary between quarries. Check the amount with your installer or the manufacturer's guidance before you order.