Aggregate calculator
Enter the length and width in metres and the depth in millimetres, pick a material, and see the volume in m³ and the weight in tonnes.
| Depth | Coverage per tonne |
|---|---|
| 20 mm | 31.3 m² |
| 50 mm | 12.5 m² |
| 75 mm | 8.3 m² |
| 100 mm | 6.2 m² |
Estimates only. Check the manufacturer's coverage rates.
How this is calculated
The volume is length x width x depth, with the depth entered in millimetres: volume (m³) = length (m) x width (m) x depth (mm) / 1000. A 5 x 3 m area at 50 mm deep is 0.75 m³.
An extra allowance, 10% by default, is added for settling and compaction. Type 1 sub-base compacts, so order extra. The volume with the allowance is then multiplied by the material's bulk density to get tonnes.
The densities are approximate: gravel (10-20 mm) 1.6 tonnes per m³, sharp sand 1.6, building sand 1.6 and Type 1 sub-base 2.1. Densities vary with moisture and supplier, so use your supplier's figure with the Custom option.
The table shows how many square metres one tonne covers at depths of 20, 50, 75 and 100 mm for the chosen material, which is handy for a quick sense check. Aggregates are sold by the tonne or bulk bag.
- Densities are approximate and vary with moisture and supplier, so use your supplier's figure.
- Aggregates are sold by the tonne or bulk bag.
- Type 1 compacts, so order extra.
Frequently asked questions
How much does a cubic metre of gravel weigh?
About 1.6 tonnes for 10-20 mm gravel, using the approximate bulk density. Densities vary with moisture and supplier, so use your supplier's figure.
How much area does 1 tonne cover?
It depends on the material and depth. Gravel at 50 mm deep covers about 12.5 m² per tonne; see the table on the calculator.
Why order extra Type 1?
Type 1 sub-base compacts when it is laid, so order extra. The calculator adds 10% by default for settling and compaction.