How many tonnes of aggregate do I need?
You calculate the quantity of aggregate in two steps: first the volume of the layer, then its weight. To convert m³ into tonnes, you need data for the specific material. There is no single value for sand, gravel and every sub-base mix.
Step 1: volume
Multiply the area by the thickness of the layer in metres. If the area varies in size or thickness, calculate each part separately. Do not mix centimetres and metres in the formula.
Worked example: an area of 50 m² and an assumed layer of 10 cm give 50 × 0.10 = 5 m³. These dimensions only show how the calculation works. They are not a recommended thickness for a driveway.
Step 2: weight
Multiply the volume by a confirmed conversion factor in t/m³. For the example above, you get 5 × the factor. Without data for the material, do not write down a result in tonnes.
The factor must refer to a known state of the aggregate. A loose layer and a compacted layer of the same weight take up different volumes. Moisture content can also change the relationship between weight and volume.
Allowance for compaction
Check whether the thickness in the design refers to the finished layer. If it does, do not simply multiply by the factor for loose material without allowing for the chosen method. Agree the compaction assumptions with your contractor.
Do not add another allowance if one is already included in your quantities. If the ground is uneven, measure the actual differences and include them in the volume.
How many loads is that?
To split the weight into deliveries, you need the actual permissible payload of the truck. It does not follow from the capacity of a truck mixer or from a description such as “a large tipper”. When you order, agree the quantity, where the load will be tipped and how the truck will get there.
We deliver aggregate by tipper truck, from a few tonnes.
Questions about quantity
How much does 1 m³ of sand or gravel weigh?
You need data for the specific material and its state. An approximate figure is no substitute for the data used to invoice sales by the tonne.
How many tonnes for a 50 m² driveway?
First decide on the layer structure and the thickness of each layer. The area alone is not enough to give a result.
Can your team check my calculation?
Include the dimensions and the material requirements in your enquiry. The final quantity should match the solution agreed with your contractor.