Garden SurveyorHow to work out how much gravel you need
Gravel is sold by weight, so start with the area you want to cover in square metres and the depth you want to lay in metres. Multiply them for the volume, then convert to tonnes using a density of roughly 1.5–1.8 tonnes per cubic metre. The calculator above handles the conversion and rounds up to whole bulk bags so you order enough to finish the job without paying for material you won't use.
Recommended gravel depths (UK)
| Use | Depth |
|---|---|
| Decorative gravel area / borders | 40–50 mm over membrane |
| Garden / informal path | 50 mm over membrane |
| Gravel driveway (top layer) | 50 mm angular over sub-base |
| Ground cover / mulch | 30–40 mm |
Always lay decorative gravel over a permeable weed-control membrane. On driveways, put angular gravel over a compacted MOT Type 1 sub-base so it stays put under traffic.
Building a whole gravel driveway?
Set out levels and falls, take off the sub-base and build a full materials list.
Frequently asked questions
- How much gravel do I need?
- Multiply the area in square metres by the depth in metres to get the volume, then multiply by roughly 1.5–1.8 tonnes per m³ depending on the stone. The calculator above does this and converts to tonnes, bulk bags and 25 kg bags so you order the right amount.
- What depth of gravel should I lay?
- For a decorative gravel area, 40–50 mm is typical over a membrane. For paths use about 50 mm, and for a gravel driveway aim for 50 mm of angular gravel over a compacted MOT Type 1 sub-base. Deeper than 50 mm of loose gravel becomes hard to walk and drive on.
- How many m² does a bulk bag of gravel cover?
- A standard bulk (jumbo) bag holds roughly 0.8 tonnes, which covers about 10–12 m² at 50 mm depth. The calculator rounds up to whole bags so you always have enough to finish.
- What's the difference between gravel, chippings and shingle?
- Chippings are angular crushed stone that lock together well — best for driveways and paths. Shingle is rounded and looser, better for decorative borders. Both are priced and ordered by tonne or bulk bag, and the calculator works for either.
- Do I need a membrane under gravel?
- Yes — lay a permeable weed-control geotextile membrane under decorative gravel to stop weeds growing through and to keep the stone from mixing into the soil below. On driveways, the membrane sits between the sub-base and the gravel.