How Much Gravel Do I Need? Tonnes, Bulk Bags and Coverage (UK)
A gravel area 5 × 4 m at 50 mm deep needs about 1.7 tonnes of 20 mm gravel, which is 3 bulk bags of 0.8 tonnes. One tonne covers about 12.5 m² at that depth. The weight depends on the stone: gravel is about 1.6 tonnes per m³, slate about 1.5 and MOT Type 1 about 2.2 when it is compacted. The gravel calculator works it out for your own area, depth and material, and the cost.
Tonnes of gravel by area and depth
For 20 mm gravel at 1.6 tonnes per m³, with 5% waste:
| Depth | 10 m² | 20 m² | 40 m² | 60 m² |
|---|---|---|---|---|
| 20 mm | 0.34 t | 0.67 t | 1.34 t | 2.02 t |
| 30 mm | 0.50 t | 1.01 t | 2.02 t | 3.02 t |
| 40 mm | 0.67 t | 1.34 t | 2.69 t | 4.03 t |
| 50 mm | 0.84 t | 1.68 t | 3.36 t | 5.04 t |
| 75 mm | 1.26 t | 2.52 t | 5.04 t | 7.56 t |
| 100 mm | 1.68 t | 3.36 t | 6.72 t | 10.08 t |
Different materials for a 5 × 4 m area at 50 mm
| Material | Weight per m³ | Tonnes | Bulk bags (0.8 t) | Area per tonne |
|---|---|---|---|---|
| 20 mm gravel or shingle | 1.6 t/m³ | 1.68 t | 3 | 12.5 m² |
| Slate or decorative chippings | 1.5 t/m³ | 1.58 t | 2 | 13.3 m² |
| Limestone chippings | 1.4 t/m³ | 1.47 t | 2 | 14.3 m² |
| Sharp or building sand | 1.7 t/m³ | 1.79 t | 3 | 11.8 m² |
| MOT Type 1 (compacted) | 2.2 t/m³ | 2.31 t | 3 | 9.1 m² |
How deep should the gravel be?
- Paths and drives: about 50 mm of gravel on top of a compacted sub-base of MOT Type 1 and a weed membrane. A thinner layer scatters and shows the base.
- Decorative borders: 30 mm is enough for a border or a bed.
- Sub-bases: 100 mm or more of MOT Type 1 under paving, and 150 mm for a drive.
- Gravel grids: a stabiliser grid keeps the gravel in place on a drive or a slope, so that it does not spread or rut.
Ordering
- Gravel is sold by the tonne, by the bulk bag and in small bags from a DIY store. Bulk bags are the cheapest way for large areas.
- Delivery is often a large part of the price, so combine your order for the sub-base, the gravel and the sand.
- Check the size: 10 mm and 14 mm gravel is smoother underfoot, and 20 mm gravel is the usual choice for a drive.
- Ask where the delivery will be left, and who will move it: a tonne of gravel is a big pile.
For paving slabs on a sub-base see the paving calculator, and for concrete see the concrete calculator. Estimates only: confirm the quantities with your supplier.
Frequently asked questions
How do I work out how much gravel I need?
Multiply the area by the depth in metres to get cubic metres, add about 5%, and multiply by the weight of a cubic metre of the material (about 1.6 tonnes for 20 mm gravel). A 5 × 4 m area at 50 mm is 1.68 tonnes.
How far does a tonne of gravel go?
A tonne covers about 12.5 m² at 50 mm deep, or twice as far at 25 mm. It depends on the material.
How much gravel for a driveway?
A drive 10 × 3 m at 50 mm deep needs about 2.5 tonnes (4 bulk bags) of gravel, on top of a sub-base of MOT Type 1.
How much gravel for a path?
A path 10 m long and 1 m wide at 50 mm deep needs about 0.8 tonnes (2 bulk bags).
What is a bulk bag of gravel?
A large bag of gravel or sand holding about 0.8 tonnes (some are 0.85). It is delivered on a pallet and lifted with a crane or a forklift, or tipped.
More guides
Tools & materials for this project
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Estimates only. Quantities depend on your materials, site and supplier. Confirm important numbers before you order, and check the Building Regulations and any planning rules for anything structural or close to a boundary.