Work out how much decorative river rock or stone you need by volume and weight for a given area and depth.
For a decorative top layer, 50mm (2in) is usually enough. For paths or areas where you want full ground cover and weed suppression, 75–100mm (3–4in) works better. Larger stones need a deeper layer to sit well.
River rock is sold by weight, so this calculator converts your volume using a typical density of 1.6 tonnes per cubic metre. Lay a weed membrane underneath and edge the area to stop stones migrating.
Multiply the area by the depth to get the volume, then convert to weight. The calculator does this and gives the result in tonnes, cubic yards and US tons.
About 50mm (2in) for decorative cover, or 75 to 100mm (3 to 4in) for paths and full ground cover. Larger stones need a deeper bed.
Around 1.6 tonnes per cubic metre, though this varies with stone size and type. The calculator uses this typical density.
Yes. A weed-control membrane stops weeds and prevents the stones working down into the soil, keeping the layer clean and even.
At 50mm deep, a tonne covers roughly 12 to 13 m². Deeper layers cover proportionally less area per tonne.
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