Gravel calculator
Work out how much gravel you need for a path, driveway or drainage layer from its area and depth, in tonnes and bags.
Result
Gravel required
Bags needed (25kg)
How to use this calculator
- Measure the length and width of the area to cover.
- Set the depth — 5cm suits a decorative top-up, 7.5–10cm suits a path or driveway sub-base.
- Read the weight required and the equivalent number of bags.
Assumptions
- Density assumed at 1.6 tonnes/m³ — actual density varies by gravel type (roughly 1.5–1.7 t/m³ for most decorative and sub-base aggregates).
- Bag count assumes a standard 25kg bag — a bulk (loose-tipped) load is far cheaper for anything over about half a tonne.
Technical details: what the fields mean
- Length
length - The longest side of the area to cover.
- Width
width - The other side of the area to cover.
- Depth
depth - Layer thickness — 5cm for a decorative top-up, 7.5–10cm for a path or driveway base.
Methodology
Volume = length × width × depth. Weight = volume × 1.6 tonnes/m³ (a typical density for compacted gravel/aggregate). Bags assume a standard 25kg bag.
Worked example
5m × 3m path, 5cm deep
Inputs: length=5, width=3, depth=5
Result: 1.20 tonnes required, 48 bags
Practical guidance
- For a driveway or heavily used path, compact a sub-base layer before adding the decorative top layer.
- A bulk bag (around 800kg–1 tonne) or loose-tipped load is much cheaper per tonne than small bags once you need more than about half a tonne.
Common mistakes
- Using a single-layer depth for a driveway, which needs a compacted sub-base as well as the visible top layer.
- Buying small bags for a large area where a bulk bag would be far cheaper.
FAQs
How much gravel do I need for a 5m x 3m path?
At 5cm deep, about 1.2 tonnes — 48 standard 25kg bags.
How deep should a gravel driveway be?
A compacted sub-base of 75–100mm, topped with a 25–50mm decorative layer, is typical for light vehicle use.