Cobbles calculator
Work out how many bulk bags of cobbles or pebbles you need.
Cobbles calculator
Use your supplier's density
You need
- Volume
- Weight
- Area
| Order by | Exact | Order, rounded up for anything sold in whole bags |
|---|
Enter your measurements to see what to order.
One cubic metre of cobbles and pebbles weighs about 1.73 tonnes and covers about 20 square metres at 50mm.
How to work out how much cobbles and pebbles you need
- Measure the area in metres and multiply length by width.
- Pick a depth in mm and multiply it by the area to get a volume.
- Multiply the volume by the bulk density, 1727 kg per cubic metre for cobbles and pebbles, to get a weight.
- Divide the weight by your supplier's tonne or bulk bag to get what to order, and round up. Suppliers do not sell part bags.
- Add 10 percent. Covers settlement, uneven ground and the material lost around the edges. A second delivery for half a yard costs more than the extra you did not use.
How many tons in a cubic yard of cobbles and pebbles?
About 1.46 US tons, at 1727 kg per cubic metre. Because published densities run from 1554 to 1900, the honest answer is a range: between 1.31 and 1.6 tons per cubic yard depending on grading and how wet the load is.
How many cubic yards in a ton of cobbles and pebbles?
About 0.69 cubic yards. One tonne is about 0.58 cubic metres.
How much does cobbles and pebbles weigh?
Between 1554 and 1900 kg per cubic metre, a spread of 22 percent. Larger stone leaves larger voids, so cobbles are quoted lighter than their rock density suggests. The calculator above uses 1727, and you can replace it with your own supplier's figure.
6 published figures from 4 suppliers, read 2026-09-20.
| Supplier | Published figure | Condition |
|---|---|---|
| Mainland Aggregates LtdUK | Approx 1.9 tonnes per cubic metre | unstated |
| Mainland Aggregates LtdUK | Approx 1.9 tonnes per cubic metre | unstated |
| Stones4GardensUK | 1,800 kg/m3 (stated for smooth pebbles) | unstated |
| Stone WarehouseUK | Cobbles up to 120mm at 100mm depth: 1.00 Bulk Bags (800kg) = 5m2 approx. | unstated |
| Stone WarehouseUK | Pebbles up to 50mm at 70mm depth: 1.360 Bulk Bags (1088kg) = 10m2 approx. | unstated |
| AWBS LtdUK | A full 850kg jumbo bulk bag will cover approximately 10-12m2 at a depth of 50mm (product is 80-120mm Scottish Cobbles) | unstated |
What you can order cobbles and pebbles in
| Pack | Where | Size |
|---|---|---|
| 850kg bulk bag | UK | 850 kg (suppliers state 700 to 1000 kg) |
| 25kg bag | UK | 25 kg |
| tonne | UK, AU | 1,000 kg |