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Gravel Driveway Tonnage Calculator

Order the right tonnage of gravel for your driveway in a single delivery.

How it is calculated

Volume is V = L × W × (D / 100), with length and width in metres and depth D in centimetres, giving V in m³. Weight is tonnes = V × ρ, where ρ is the bulk density in tonnes per m³. Length, width and depth must be above zero. If you leave density blank the tool uses 1.6 t/m³; if you type a density that is zero, negative or above 5 t/m³ (denser than any real aggregate) there is no result. Bulk bags are counted as ceil(tonnes / 0.85), which assumes an 850 kg bag and rounds up to a whole bag. The calculation covers a flat rectangle at one even depth. Compaction, edge waste and sloping ground are not added, so any allowance on top is your own judgement.

Worked example

A driveway 12 m long and 3.5 m wide, laid 10 cm deep, gravel density 1.7 t/m³. Volume = 12 × 3.5 × 0.10 = 4.20 m³. Weight = 4.20 × 1.7 = 7.14 t. Bulk bags = 7.14 / 0.85 = 8.4, rounded up to 9 bags of 850 kg each. Nine bags hold 7.65 t, so about half a tonne is spare. With the density left blank, the default 1.6 gives 6.72 t and 8 bags.

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Common mistakes

  • Entering the depth in metres or millimetres. The field is in centimetres, so 10 means 10 cm, and 0.1 would be treated as one millimetre.
  • Leaving density blank and not noticing that 1.6 t/m³ was used. Check your supplier's figure for the stone you are ordering, because lighter or heavier stone moves the tonnage.
  • Typing a density in kg/m³, such as 1600. Anything above 5 gives no result; the field is in tonnes per m³, so enter 1.6.
  • Using the loose density for compacted gravel, or the other way round. Settled material needs more weight for the same finished depth.
  • Ordering exactly the tonnage shown. Bags are rounded up, but a bulk delivery has no such cushion, so think about waste and uneven ground.

About this calculator

Gravel tonnage is found by first calculating the volume needed — driveway area × depth — then multiplying by the bulk density of the gravel, which typically runs around 1.5–1.7 tonnes per cubic meter for compacted crushed stone. Dividing that total tonnage by the capacity of a bulk bag, commonly around 800–1,000 kg, gives the number of bags to order.

Homeowners and landscaping contractors run this calculation before ordering because gravel is usually sold and delivered by weight, not volume, and getting the tonnage wrong means either an expensive second delivery or costly leftover material — both worth avoiding on a job where delivery charges alone can be significant. Getting the depth right matters as much as the area: a driveway sub-base typically needs a deeper layer than a decorative top-dressing layer, and mixing up the two is a common source of underestimating.

Gravel density defaults to 1.6 t/m³ when left blank, and the bulk-bag count assumes 850 kg bags, rounded up to whole bags.

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