Pea Gravel Calculator
Works out pea gravel for a path, border or play area. Pea gravel is rounded and small, which changes both the depth worth laying and where it is a good idea.
Includes the waste allowance — this is the figure to order.
Share sends a link that reopens these numbers. Copy details pastes the full breakdown as a list.
The formula
volume = length × width × depth × (1 + waste) weight = volume × bulk density
The geometry is trivial; the bulk density is where the answer actually comes from. Pea gravel runs about 1700 kg per cubic metre loose, so a cubic metre weighs roughly 1.70 tonnes. Suppliers quote one or the other, which is why both are given.
What to watch out for
Pea gravel behaves differently from angular stone, and that drives every decision:
- It rolls. Rounded stones do not interlock, so the surface stays loose. Lovely underfoot in a border, awkward on a slope and poor under vehicles.
- Shallow is better. 30–50 mm. Deeper just means you sink into it.
- It needs an edge. With nothing to contain it, pea gravel spreads. A border edging or buried timber keeps it where you put it.
Frequently Asked Questions
How deep should pea gravel be?
30–50 mm for a path or border. It does not lock together, so a deeper layer simply means your feet sink further into it.
How much area does a bulk bag of pea gravel cover?
About 850 kg, or half a cubic metre. At 40 mm deep that covers roughly 12 m².
Can I use pea gravel on a driveway?
Not ideally. The rounded shape means it shifts under tyres, forms ridges and ends up on the lawn. Angular 10–20 mm stone holds together far better.