How area and depth become a material quantity
The calculator converts the entered area and depth to square metres and metres. Area multiplied by depth gives the geometric volume. The selected allowance is then added before volume is multiplied by the entered bulk density.
order volume = net volume × (1 + allowance ÷ 100)
mass = order volume × bulk density
For US customary inputs, square feet, inches and pounds per cubic foot are normalised internally. Results are shown in both cubic metres/cubic yards and metric tonnes/US short tons.
Indicative density starting points
These values are deliberately editable. They are not material certificates and should not override a project specification or supplier declaration.
| Material | Preset kg/m³ | Approx. lb/ft³ | Basis |
|---|---|---|---|
| Type 1 sub-base | 2,200 | 137.3 | Compacted |
| 6F2 recycled aggregate | 2,000 | 124.9 | Compacted |
| Asphalt / tarmac | 2,350 | 146.7 | Laid |
| Normal concrete | 2,400 | 149.8 | Hardened |
| Gravel / shingle | 1,650 | 103.0 | Loose |
| Dry construction sand | 1,600 | 99.9 | Loose |
| Screened topsoil | 1,300 | 81.2 | Loose |
Choosing an allowance
An allowance may cover level variation, compaction, trimming, contamination and ordering increments. It is not a substitute for converting a loose supplier volume to a specified compacted volume. Keep that distinction explicit.
Frequently asked questions
How do I calculate tonnes of aggregate from area and depth?
Multiply area by depth to obtain volume, add the chosen allowance, then multiply by a verified bulk density. Divide kilograms by 1,000 for metric tonnes.
Are the material densities exact?
No. Actual bulk density changes with grading, source, moisture, voids and compaction. Replace the presets with supplier or test data wherever available.
What is the difference between a tonne and a short ton?
A metric tonne is 1,000 kg. A US short ton is 2,000 lb, approximately 907.185 kg.