Sub-base calculator: how much MOT Type 1 do I need?

Put in the length, width and depth of your driveway, patio or slab base. You'll see the volume, the tonnes to order and roughly how many bulk bags that comes to.

How it works

1. 1Measure the length and width of the area in metres. For an L-shape or odd shape, split it into rectangles and run each through separately.
2. 2Pick your depth. 100mm is usual for a patio or path, 150mm for a domestic driveway, and 200mm or more where vehicles will sit on it regularly.
3. 3Add a spare allowance. 10% covers compaction and uneven ground; go 15% if the dig-out is rough.
4. 4Check the tonnes against the bulk bags. A bulk bag of MOT Type 1 holds around 850kg, so a tonne is a bit more than one bag.
5. 5Order a little over. Running short mid-job means a second delivery charge, which usually costs more than the extra half tonne.

How deep should a sub-base be?

• Patios and paths — 100mm of compacted MOT Type 1 is the usual spec on decent ground.
• Domestic driveways — 150mm is the common figure for cars; go deeper on soft or clay ground.
• Heavy use — 200mm+ where vans or heavier vehicles will park regularly.

Tonnes per cubic metre

MOT Type 1 and scalpings weigh roughly 2 tonnes per compacted cubic metre; recycled hardcore runs a bit lighter at about 1.9. These are rough trade guides only — density changes with moisture and supplier, so treat the figures as a ballpark and confirm with your merchant before ordering.

Quantities are typical trade allowances and a guide only — always confirm with your tradesperson or supplier before ordering.

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