River Rock Calculator
Tons and bags of decorative river rock for a bed, by depth and stone size.
Decorative stone is sold by weight and installed by volume, which is why the bag label and the landscaping plan never quite agree. A cubic yard of river rock weighs somewhere between 1.25 and 1.4 tons depending on how rounded and how large the stones are, and that 10% difference is a whole extra load on a big bed.
Depth is the other variable people get wrong. Two inches of small river rock looks finished; two inches of four inch stones looks like scattered gravel with soil showing between them. The rule is to use a depth roughly equal to the stone size, which means larger stone costs more in volume as well as more per ton.
How this calculator works
Every field is editable and the result updates as you type — nothing is submitted anywhere, all the maths runs in your browser. That matters for a number you are about to spend money on: you can see exactly which input moved the answer, and by how much.
What this calculation assumes
Assumes a level bed on weed fabric and density figures typical of rounded river stone. Wet stone, flat slate chips and angular crushed rock all weigh differently, so confirm tons per cubic yard with the supplier before ordering bulk.
Treat the result as an order-of-magnitude check rather than a final quantity. Product packaging changes, regional labour rates vary by a factor of two, and no calculator has seen your actual site.
Frequently asked questions
How deep should river rock be?
Two inches for one to three inch stone, three inches for three to five inch stone. Deeper than that is usually wasted material — the point is to hide the soil and the weed fabric beneath, not to build up a layer. On slopes, go one size larger rather than deeper.
Tons or bags?
Bags for anything under about half a cubic yard, bulk by the ton above that. Bags cost several times more per cubic foot, and on a bed this size you would be carrying dozens of them. Bulk delivery also means a pile on the driveway that has to be moved by hand anyway.
Do I need weed fabric underneath?
Yes, a woven geotextile, not the thin spun material. River rock alone does not stop weeds, and it makes weeding harder because every pulled weed brings a shower of stones with it. Fabric also stops the stone from sinking into the soil over a few seasons.
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