Free MOT Type 1, crushed concrete and sub-base estimator for tonnes, bulk bags, depth and project cost.
Use this Hardcore Calculator UK to estimate the quantity of MOT Type 1, crushed concrete, 6F2 hardcore or general sub-base aggregate required for a driveway, patio, garden path, shed base, garage base, trench backfill or hardstanding. Enter your area size, depth and material type, then the calculator will estimate cubic metres, tonnes, bulk bags, 25kg bags and a practical wastage allowance.
```A good sub-base is one of the most important hidden parts of any driveway, patio, paving area, shed base or concrete slab. The finished surface is what people see, but the hardcore underneath is what spreads the load, supports the surface, reduces settlement and helps the project stay level for longer. If the hardcore layer is too thin, poorly compacted or under-ordered, the surface can dip, crack, rock, hold water or become uneven after traffic and weather.
```This Hardcore Calculator UK is designed for homeowners, landscapers, builders, groundwork contractors and DIY users who need a quick way to estimate sub-base material before ordering from a local aggregate supplier. It works for MOT Type 1, DTp1, crushed concrete, recycled aggregate, 6F2 fill and general compacted hardcore. You can calculate the required volume in cubic metres, convert that into tonnes, estimate bulk bags and add a practical wastage allowance for compaction, trimming, uneven ground and small site losses.
Hardcore is often ordered by the tonne, but most site measurements are taken in metres and millimetres. That is why many people under-order. A driveway might look small at ground level, but at 150mm compacted depth it can require several tonnes of sub-base before the finished surface is even started. The calculator bridges that gap by converting length, width and depth into a realistic tonnage estimate.
MOT Type 1 or properly graded crushed concrete is commonly used where a firm load-bearing sub-base is needed for cars and light vans.
Many domestic projects use around 75mm for paths, 100mm for patios and 150mm for driveways, depending on ground conditions.
Most bulk bags are sold as approximately 0.8 to 0.9 tonnes, so the calculator lets you adjust the bag size before ordering.
A 10% allowance is useful for uneven excavation, edge trimming, compaction loss and small measuring errors on site.
To use the calculator, measure the area that will receive hardcore or sub-base. For a simple rectangle, measure the length and width in metres. Then choose the compacted depth in millimetres. The calculator multiplies the area by the depth to calculate cubic metres, then converts that volume into tonnes using the selected material density.
```For example, a 6m by 3m driveway has an area of 18m². If you want a 150mm compacted MOT Type 1 sub-base, the compacted volume is 2.7m³. After applying a density of around 2.1 tonnes per cubic metre and adding a 10% allowance, the order quantity becomes a little over 6 tonnes. This is why even a small driveway often needs more material than expected.
If your project is not rectangular, split it into smaller rectangles and calculate each section separately. For an L-shaped driveway, calculate the large rectangle first, then the smaller side rectangle, and add both results together. For curved garden paths, use an average width multiplied by the total path length. For trenches, multiply trench length by width by depth, then select a general fill or crushed concrete density.
The calculator is designed as an estimating tool, not a replacement for site judgement. Ground conditions, soft spots, clay, drainage, slope, edge restraints and vehicle loading all affect the final sub-base design. If the ground is weak, waterlogged or expected to carry heavy vehicles, use a deeper sub-base and ask a qualified contractor or structural engineer for project-specific advice.
The basic hardcore calculation is simple:
Length × Width × Depth = Volume in cubic metres
Volume × Material Density = Tonnes Required
Tonnes × Wastage Allowance = Order Quantity
| Measurement | Example | Why It Matters |
|---|---|---|
| Length | 6 metres | Longer areas quickly increase the cubic metre requirement. |
| Width | 3 metres | Width is often underestimated on driveways because of edge restraints and turning space. |
| Depth | 150mm | Depth has a major effect. Doubling the depth doubles the volume and tonnage. |
| Density | 1.6 to 2.1 t/m³ | Dense MOT Type 1 normally weighs more per cubic metre than loose oversized fill. |
| Wastage | 5% to 15% | Allows for compaction, uneven ground, spreading losses and edge trimming. |
In UK construction, the word hardcore usually describes a compacted layer of crushed stone, crushed concrete, brick rubble or graded sub-base material placed below a finished surface. It is used to create a strong, stable foundation layer for driveways, paths, patios, concrete slabs, shed bases, garages and other hardstanding areas. The exact material varies by supplier, but the purpose is always similar: spread loads, fill levels, reduce movement and provide a firm base.
```The term is sometimes used loosely. One builder might say hardcore and mean MOT Type 1. Another might mean crushed concrete. Another might mean 6F2 recycled demolition aggregate used as bulk fill. For accurate ordering, it is better to choose the actual material name rather than simply asking for hardcore. If you need a finished sub-base below block paving, tarmac, concrete or paving slabs, MOT Type 1 or a certified Type 1 recycled aggregate is usually the safer choice. If you need to raise levels below a large slab, 6F2 or crushed concrete may be used as a lower fill layer before a finer top layer is compacted above.
Hardcore should be clean, angular and compactable. Angular particles lock together when compacted, creating a more stable base than rounded gravel. Material containing too much soil, timber, plaster, metal or organic waste should not be used as a structural sub-base. Poor-quality fill can break down, hold water, smell, settle unevenly or fail to compact properly.
MOT Type 1 is a specific type of well-graded sub-base aggregate. It normally contains crushed rock, limestone, granite or recycled crushed concrete graded up to around 40mm with smaller particles and fines. Those fines help the material bind tightly when compacted. General hardcore can be less controlled and may contain a wider mix of crushed materials. That does not always make it unsuitable, but it does mean the result depends heavily on the supplier and grading.
For driveways and patios, MOT Type 1 is usually preferred because it compacts into a firm, dense layer. For deep fill, oversized crushed concrete or 6F2 may be more economical, but it normally needs a finer regulating layer above it. When in doubt, use Type 1 for the final compacted sub-base and only use larger hardcore as a lower fill layer where appropriate.
```The correct hardcore depth depends on the finished surface, ground condition and load. A light garden path needs less support than a driveway used by cars. A patio on firm ground needs less depth than a driveway crossing soft clay. The figures below are practical domestic starting points, not strict engineering specifications.
```| Project | Typical Compacted Depth | Recommended Material | Notes |
|---|---|---|---|
| Garden path | 75mm | MOT Type 1 or compacted crushed stone | Suitable for pedestrian traffic on reasonably firm ground. |
| Patio / paving area | 100mm | MOT Type 1 | Use a compacted sub-base below the bedding layer for paving slabs. |
| Driveway for cars | 150mm | MOT Type 1 or certified Type 1 recycled aggregate | May need more depth on soft ground or where vans will park regularly. |
| Shed base | 75mm to 100mm | Type 1 or crushed concrete | Depth depends on shed size, ground condition and whether a concrete slab follows. |
| Concrete slab base | 100mm to 150mm | Compacted Type 1 | Often used below slabs for garages, extensions, workshops and bases. |
| Heavy use / poor ground | 200mm+ | Engineered sub-base specification | Professional design may be needed for heavy loads, clay, drainage issues or commercial use. |
Important: The depth entered into the calculator should be the finished compacted depth, not the loose tipped depth. Loose aggregate reduces in height when compacted with a plate compactor or roller, so include a wastage/compaction allowance when ordering.
For most domestic jobs, compact the sub-base in layers rather than tipping the full depth and trying to compact it all at once. A plate compactor works better when each layer is placed, levelled and compacted before the next layer is added. For thicker driveways, two compacted layers may perform better than one deep layer. This helps avoid soft pockets and improves load distribution.
```Hardcore and sub-base materials are usually sold by the tonne, but your excavation volume is measured in cubic metres. The conversion depends on density. Dense MOT Type 1 is heavier than loose oversized rubble. Recycled crushed concrete can vary depending on grading, moisture and source. This calculator uses sensible UK estimating values, but your supplier may quote a different density for their own product.
```| Material | Calculator Density | Best Use |
|---|---|---|
| MOT Type 1 / DTp1 | 2.1 tonnes per m³ | Driveways, patios, paving, hardstanding, structural sub-base. |
| Crushed concrete hardcore | 1.9 tonnes per m³ | Sub-base, fill, recycled construction aggregate, general groundwork. |
| Recycled aggregate sub-base | 1.8 tonnes per m³ | Budget-friendly sub-base where certified recycled material is acceptable. |
| 6F2 crushed hardcore | 1.7 tonnes per m³ | Bulk fill, raising levels, lower layers before a finer regulating layer. |
| General compacted hardcore | 1.6 tonnes per m³ | Basic fill estimate when exact supplier density is unknown. |
Because density changes by supplier, do not treat any online calculator as a purchase guarantee. Use the result to plan your order, then confirm with your local quarry, builder’s merchant or aggregate supplier. If their bulk bag is 0.8 tonnes instead of 0.85 tonnes, or their Type 1 density is different, adjust the calculator inputs before ordering.
Small domestic users often buy hardcore in bulk bags. A bulk bag is convenient, clean and easy to place on a driveway, but it is usually more expensive per tonne than a loose tipped load. Larger jobs often become cheaper with loose delivery, especially when the supplier can tip directly near the work area. If access is tight, a hiab delivery or bulk bags may still be more practical.
As a rough planning rule, one 0.85 tonne bulk bag of MOT Type 1 may cover around 4m² to 5m² at 100mm compacted depth depending on density and compaction. At 150mm driveway depth, the same bag covers much less. This is why a driveway that looks modest can require several bulk bags or a loose load.
```The best material depends on what you are building. A patio does not need the same sub-base as a farm track, and a decorative gravel area does not need the same foundation as a concrete driveway. Choosing the correct material helps avoid wasted money and future settlement.
```MOT Type 1 is the most common sub-base choice for many domestic driveways, patios and paving areas. It is crushed, graded and contains fine particles that help it compact into a firm surface. It is often used below block paving, concrete, tarmac, resin-bound systems and paving slabs. Where a strong non-permeable or conventional sub-base is acceptable, Type 1 is a reliable option.
Crushed concrete is popular because it is often cheaper than quarried stone and makes use of recycled material. Good-quality crushed concrete can work well as a sub-base, especially when it is graded and free from contamination. However, quality varies. Avoid material with too much brick, plaster, timber, soil or mixed waste. For a driveway or slab, ask for a graded product suitable for compaction.
6F2 is usually a larger recycled aggregate used for bulk fill, haul roads, raising levels and lower sub-base layers. It can be useful when you need to fill a deeper excavation economically. However, because it contains larger pieces, it may not provide the smooth, tight finish required directly below paving. Many contractors use 6F2 as a lower layer and then cap it with MOT Type 1.
Recycled Type 1 can be a cost-effective and more sustainable alternative to primary quarried Type 1. It is normally made from crushed concrete and other approved recycled materials, screened to a suitable grading. The key is certification and consistency. If the supplier provides a Type 1 recycled aggregate suitable for sub-base use, it can be a good option for many domestic projects.
MOT Type 3 is different from MOT Type 1 because it is open-graded and more permeable. For permeable block paving, resin-bound driveways or SuDS-sensitive front garden work, Type 3 or another free-draining sub-base may be needed. Standard MOT Type 1 contains fines and does not drain as freely. If your driveway must be permeable, check the design before ordering ordinary hardcore.
```Driveways place more demand on sub-base material than patios or paths because cars create repeated point loads. Turning wheels, braking, parking in the same position and wet ground all increase pressure on the sub-base. If the hardcore layer is too shallow, the driveway can rut or sink, especially near entrances, wheel tracks and edges.
```For a normal domestic driveway carrying cars, 150mm of compacted MOT Type 1 is a common starting point. On firm, well-drained ground this may be enough for many projects. On soft clay, made-up ground, poor drainage or where vans will park, more depth may be required. A geotextile membrane can help separate the sub-base from the soil below, reducing migration of fines and improving long-term stability.
Excavation depth should allow for the sub-base, bedding layer and finished surface. For example, a block paved driveway might include the paving blocks, a sharp sand bedding layer and a compacted Type 1 layer. A gravel driveway might include geotextile membrane, compacted sub-base and decorative gravel above. Always calculate the full build-up before digging so the finished surface meets doors, thresholds, kerbs and drainage falls correctly.
Edge restraints are also important. Even a good hardcore layer can move sideways if the edges are unsupported. Kerbs, edging stones, concrete haunching or timber restraints help keep the sub-base and surface material contained. Without edge restraint, gravel spreads, paving moves and the sub-base can loosen at the sides.
```Patios and garden paths usually carry lighter loads than driveways, but they still need a stable base. A patio laid on weak or poorly compacted ground can rock, hold water or develop uneven joints. A compacted sub-base helps distribute loads and keeps the bedding layer more consistent.
```For patios, 100mm of compacted MOT Type 1 is a common domestic depth. This is usually followed by a full mortar bed or suitable bedding layer, depending on the paving system. For paths, 75mm may be enough where the ground is firm and the path is pedestrian-only. If the path crosses soft ground, receives wheelbarrow traffic or forms part of a garden access route, a deeper sub-base may be sensible.
Shed bases vary widely. A small timber shed on a firm garden may only need a modest compacted stone base and paving slabs. A larger workshop, garden office or concrete slab base may need a deeper, more carefully prepared sub-base. The heavier the structure, the more important the ground preparation becomes. If the base will support expensive equipment, insulated panels or a habitable garden room, do not rely on a shallow layer of loose rubble.
Good preparation matters more than simply ordering enough tonnes. Remove soft topsoil, roots and organic material. Level and compact the formation before placing hardcore. Lay a membrane if separation is needed. Spread the material evenly and compact in layers. Check levels with a straight edge, string line or laser level before adding the final surface.
```One of the most common mistakes is using centimetres or millimetres incorrectly in the calculation. A 100mm depth is 0.1 metres, not 1 metre. The calculator handles the conversion automatically, but manual calculations often go wrong at this step. Another common mistake is forgetting compaction. Loose hardcore will reduce in height after compacting, so the delivered quantity must account for the finished compacted depth.
```Another mistake is assuming all bulk bags contain one full tonne. Many bulk bags are closer to 0.8 or 0.85 tonnes, although this depends on product and supplier. If the calculator says you need 4 tonnes, four bulk bags may not be enough. Adjust the bulk bag size field to match the supplier’s bag weight.
People also underestimate irregular shapes. A driveway with a curved edge, splayed entrance or side parking bay may have more area than a simple measurement suggests. For irregular areas, break the site into smaller rectangles and add a little extra allowance. Ordering slightly too much is usually less disruptive than stopping halfway through a job and paying another delivery charge for a small top-up.
Finally, do not order the cheapest “hardcore” without knowing what it contains. Dirty mixed rubble can be difficult to compact and may include unwanted contaminants. For driveways, patios and concrete slabs, a clean graded sub-base is usually worth the extra cost.
```Hardcore costs vary by region, aggregate type, delivery distance, order size and whether you buy loose tonnes or bulk bags. Primary MOT Type 1 is usually more expensive than recycled crushed concrete. Bulk bags are convenient for small jobs but often cost more per tonne than a loose tipped load. Delivery can also make a big difference, especially for small orders.
```| Material | Typical Use | Relative Cost | Ordering Tip |
|---|---|---|---|
| MOT Type 1 | Driveways, patios, paving, slabs | Medium | Best all-round choice where a compacted sub-base is needed. |
| Crushed concrete | Recycled sub-base and general fill | Low to medium | Check it is clean, graded and suitable for compaction. |
| 6F2 hardcore | Bulk fill and deep build-ups | Low | Often needs Type 1 above for a tighter finish. |
| Recycled Type 1 | Sub-base where recycled material is acceptable | Low to medium | Ask for specification and grading details before ordering. |
| Bulk bags | Small domestic jobs with limited access | Higher per tonne | Useful where loose tipping is not possible. |
The calculator includes a price per tonne field so you can enter your local quote. For a more accurate total, add delivery, VAT, membrane, skips, labour, plate compactor hire and any edge restraints. Material cost alone is only part of the project cost.
```Correct compaction is just as important as the quantity of hardcore. Spread the material evenly and compact it with a vibrating plate compactor or roller. Do not rely on walking over the material or driving over it a few times. Proper compaction locks the aggregate together and reduces future settlement.
```If water sits in the excavation before you place the hardcore, solve the drainage issue first. A strong sub-base cannot perform properly if it is sitting in a saturated, unstable formation. On drainage-sensitive front garden driveways, check whether a permeable build-up is required before choosing standard MOT Type 1.
```Useful related calculators: MOT Type 1 Calculator | Type 1 Sub-Base Calculator | Gravel Calculator UK | Crushed Stone Calculator | Recycled Aggregate Calculator UK | Concrete Mix Calculator UK | Building Cost per Square Metre UK
Measure the length and width of the area in metres, multiply them to get square metres, then multiply by the required depth in metres. After that, multiply by the density of your chosen hardcore material to convert cubic metres into tonnes. For a quick estimate, use the calculator above and add a 10% wastage or compaction allowance.
For a normal domestic driveway used by cars, 150mm of compacted MOT Type 1 is a common starting point. Soft ground, clay, poor drainage, vans or repeated heavy loading may require a deeper sub-base. Always compact the material properly and use suitable edge restraints.
A patio commonly uses around 100mm of compacted MOT Type 1 below the bedding layer. The final depth depends on ground condition, paving type, drainage and the total build-up. The sub-base should be level, firm and compacted before the bedding layer is installed.
For a pedestrian garden path on firm ground, around 75mm of compacted sub-base is often used. If the path crosses soft ground, carries wheelbarrows or forms a main access route, a deeper layer may be worthwhile.
Hardcore is a general term for crushed fill or sub-base material. MOT Type 1 is a more specific graded sub-base with a controlled range of particle sizes and fines that help it compact tightly. For driveways, patios and paving, Type 1 is usually more predictable than unspecified mixed hardcore.
Many bulk bags contain around 0.8 to 0.9 tonnes, but this depends on the supplier and product. Some merchants sell “bulk bags” by approximate weight rather than a fixed full tonne. Check the supplier’s bag weight and enter it into the calculator before ordering.
Divide the total tonnes required by the weight of one bulk bag. For example, if the calculator estimates 3.4 tonnes and your supplier’s bulk bag is 0.85 tonnes, you need 4 bulk bags. Always round up because ordering half a bag is not normally possible.
Coverage depends on depth and density. At 100mm compacted depth, one tonne of dense Type 1 may cover roughly 4m² to 5m². At 150mm driveway depth it covers less. Use the calculator for your exact length, width, depth and selected density.
A geotextile membrane is often useful between the soil and sub-base, especially on soft ground, clay or areas where fines may migrate. It helps separate the sub-base from the formation below. It is not a substitute for proper excavation and compaction, but it can improve long-term stability.
Yes, crushed concrete can be suitable if it is clean, graded and appropriate for sub-base use. It is often cheaper and uses recycled material. For paving or driveways, avoid dirty mixed rubble and ask the supplier whether the product is suitable for compaction.
MOT Type 1 contains fines that help it compact into a dense layer, so it is not normally considered a free-draining permeable sub-base. For permeable driveways or SuDS-sensitive work, an open-graded material such as Type 3 may be required instead.
For a gravel driveway or path, a compacted sub-base can sit below a decorative gravel layer. A membrane may be used between layers depending on the design. Do not rely on loose hardcore as the finished surface because it is uncomfortable underfoot, hard to maintain and may contain large sharp particles.
Hardcore should be moist enough to help fines bind, but not saturated. Very dry material can be dusty and harder to compact; waterlogged material can pump, move or fail to lock together. Light dampening may help in dry weather, but standing water should be dealt with before compaction.
Split the L-shape into two rectangles. Calculate the length, width and depth for each rectangle, then add the results together. Add a wastage allowance after combining the areas. This method is more accurate than guessing an average size for an irregular shape.
Clean crushed brick and concrete may be used in some fill situations, but random rubble is not ideal for a reliable sub-base. It may contain soft material, plaster, timber, soil or voids that prevent proper compaction. For driveways, slabs and patios, a graded aggregate is usually the safer choice.
For most domestic projects, add around 10%. Increase the allowance if the excavation is uneven, the ground is soft, the area is irregular or you are unsure about levels. Ordering a little extra is often cheaper than paying a second delivery charge for a small shortage.
Yes, you can use it for a simple trench volume estimate by entering trench length, width and depth. Choose a suitable material type and density. For drainage trenches, pipe bedding or structural backfill, follow the project specification because material type and compaction requirements may be different.
This calculator is suitable for estimating material quantities, ordering aggregates and planning domestic projects. It is not a structural design tool. Heavy loading, commercial yards, highways, retaining structures and poor ground conditions should be checked by a qualified professional.