Gravel Calculator
Work out how many tonnes of gravel, MOT Type 1 or sand you need for a driveway, path or base, and how many bulk bags or small bags that is.
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- Weight to order
- 1.68 tonnes
- Volume
- 0.99 m³
- Bulk bags (about 850 kg)
- 2 bags
- Or small bags (20 kg)
- 85 bags
- Area
- 18 m²
What it does
Find how much gravel, sub-base or sand you need to cover an area to a set depth. Enter the length, width and depth, choose the material, and see the weight to order in tonnes, the volume, and how many bulk bags or 20 kg bags that is.
How to use it
- Length
The length of the area to cover.
- Width
The width of the area. For curved or odd shapes, use the area calculator first and enter the area as length × 1.
- Depth
Decorative gravel: 30 to 50 mm (deeper is hard to walk on). Driveway gravel: about 50 mm, on a sub-base. MOT Type 1 sub-base: 100 mm for paths and patios, 150 mm or more for driveways.
- Material
Gravel, shingle and chippings about 1.7 tonnes per m³; MOT Type 1 sub-base about 2.1 compacted; sharp or building sand about 1.6.
- Density
Tonnes per cubic metre, from the supplier. Most stone and sand is 1.4 to 2.2.
- Extra
For uneven ground, settling and spreading. Allow more for sub-base that will be compacted with a wacker plate.
Common uses
- Gravelling a driveway, path or parking area.
- Laying MOT Type 1 sub-base under a patio, shed base or driveway.
- Topping a border or garden with decorative stone.
- Working out the concrete for a slab on top. Try the Concrete Calculator
- Working out the area of a curved or odd shape. Try the Area Calculator
The formula
Volume = length × width × depth × (1 + extra ÷ 100)Weight = volume × densityBags = weight ÷ bag weight, rounded upWhere:
- density
- gravel about 1.7 t/m³, MOT Type 1 about 2.1 t/m³ compacted, sand about 1.6 t/m³
Densities vary with the stone and how wet it is, so treat the weight as a close estimate. Suppliers sell by the tonne or by the bulk bag; bulk bags range from about 800 kg to a tonne.
Worked example
Gravel 50 mm deep over 6 m by 3 m:
- Volume: 6 m × 3 m × 0.05 m = 0.9 m³
- Plus 10%: 0.99 m³
- Weight: 0.99 m³ × 1.7 t/m³ = 1.68 tonnes
- That's 2 bags of about 850 kg, or 85 bags of 20 kg
Questions people ask
How deep should gravel be?
30 to 50 mm for paths and decorative areas; any deeper and it's hard to walk or push a wheelbarrow through. Driveways need about 50 mm of gravel (often 10 to 20 mm stone) on 100 to 150 mm of compacted sub-base, with a weed membrane in between.
How much does a bulk bag of gravel cover?
A typical 850 kg bulk bag of gravel covers about 10 m² at 50 mm deep, or about 17 m² at 30 mm.
What is MOT Type 1?
A crushed stone sub-base, graded from 40 mm down to dust, that compacts into a firm layer. It's used under driveways, patios and paths. Order about 10 to 20% more than the loose volume, because it compacts down.
Last checked 1 November 2026 · Last rev. 31 October 2026 · 22a5