Aggregate assumptions
Gravel density and stone type
Adjust density when the aggregate type or supplier data differs from the default.
Why pea gravel, slate chippings, cobbles, and sub-base materials can produce different tonne and bag estimates.
Volume is not the whole order
The area and depth tell you the volume, but most suppliers sell gravel by weight. Density is the bridge between the two. A lightweight decorative chipping and a dense sub-base can have the same cubic metre volume but different tonne estimates.
- Use the aggregate preset only as a starting point.
- Override density when the supplier gives a specific figure.
- Compare tonnes and bag count after changing density, not just volume.
Stone size affects appearance and handling
Larger stones may need a deeper layer to look even, while small chippings can settle into gaps more readily. The calculator cannot inspect the stone shape or the site conditions, so use it to price and compare options, then confirm practical suitability with the supplier.
- Check the product's suggested use before choosing depth.
- Avoid sharp or unsuitable aggregates in areas where people or pets may walk barefoot.
- Keep decorative preference separate from structural requirements.
Density-sensitive inputs
| Input | Effect on result | Best source |
|---|---|---|
| Density | Changes tonnes and bags | Supplier or product data. |
| Bag size | Changes rounded bag count | Product listing or quote. |
| Depth | Changes volume directly | Project build-up and finish requirement. |
This is an estimate. Site conditions, compaction, and aggregate type can change the final quantity.