How Much Hardcore Do I Need Per m²? (With Calculator)

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Hardcore Calculator

Work out how much hardcore you need for your sub-base in tonnes. You can enter the area directly, or let the calculator work it out for you.

✔ How to Calculate Hardcore for Any Area

  1. 1

    Measure the Area in m²

    Start by measuring the total area you need to cover. If the shape is a simple square or rectangle, multiply the length by the width in metres. For irregular shapes, break them into sections and add them together. If you’re not sure of your area, our calculator above can help you work it out using basic dimensions.

  2. 2

    Choose Your Required Depth

    Different projects need different depths of hardcore. For example, patios might need 75–100mm, while driveways need 150mm or more. Make sure you’re using the correct figure based on what you’re building. Always measure depth in millimetres at this stage — you’ll convert it later in the next step.

  3. 3

    Convert Depth to Metres and Multiply

    Convert your depth from millimetres to metres by dividing by 1,000. For example, 100mm becomes 0.1 metres. Then multiply your area in square metres by your depth in metres. This gives you the total volume in cubic metres (m³) — the amount of hardcore you'll need before converting it into weight.

  4. 4

    Multiply Volume by 2.4 for Tonnes

    MOT Type 1 hardcore weighs roughly 2.4 tonnes per cubic metre. Multiply your volume (in m³) by 2.4 to get an estimate in tonnes. For example, if your volume is 2.5 m³, you'll need around 6 tonnes of hardcore. This gives you a solid estimate based on compacted weight.

  5. 5

    Round Up and Add 10% for Waste

    Always round up slightly and add around 10% to your total to account for settlement, compaction gaps, and minor miscalculations. It’s better to have a bit extra than run short mid-job. This buffer helps ensure full coverage and allows for any last-minute depth adjustments or patching.

Common Hardcore Depths by Project

  • ✔ Garden patio or path: 75–100mm

    For light-use areas like patios and footpaths, a hardcore depth of 75–100mm is usually enough. This provides a stable base without overbuilding and keeps digging to a manageable level. Always compact the hardcore in layers to avoid future movement or dips.
  • ✔ Shed base: 100–150mm

    A small to medium shed needs a more substantial base to prevent shifting or sinking. 100–150mm of compacted MOT Type 1 gives you good load distribution for timber or concrete foundations, especially if the ground is soft or uneven.
  • ✔ Driveway (cars): 150mm

    For standard driveways that will support car traffic, a 150mm compacted hardcore layer is recommended. This ensures strength and longevity under regular vehicle weight, especially when paired with a solid sub-base and surface layer.
  • ✔ Driveway (heavier loads): 200mm+

    If you’re parking vans, 4x4s, or delivery vehicles, you’ll want 200mm or more of hardcore. This gives extra load-bearing strength and reduces the risk of rutting or cracking in the finished surface. More depth = more durability.
  • ✔ Artificial grass base: 50–75mm

    For artificial grass, a thinner hardcore layer is typically fine — 50 to 75mm is enough if the soil underneath is well-drained. Add a layer of sharp sand or granite dust above it for levelling before laying the turf.

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