How Much River Rock for a 20×20 bed?
This calculator is pre-filled to estimate the river rock for a 20×20 bed. Change any field to match your project, and enter your local price for a precise cost.
Quick answer: A 20×20 bed at a 2 in depth needs about 3.6 tons of river rock (2.59 cubic yards).
River Rock calculator
How it's calculated: Length ft × width ft × (depth in ÷ 12) = cubic feet; add 5% waste and divide by 27 for cubic yards, then multiply by 1.4 tons per cubic yard.
How to estimate river rock
- Lay landscape fabric under decorative rock to slow weeds and keep stone from sinking into soil.
- 2 inches covers for looks; 3-4 inches if you want full weed suppression and no soil showing.
- Larger stone needs a slightly deeper layer to fully hide the ground beneath.
- Buy the full amount from one supplier in one order - river rock color varies by source and a second load may not match.
- Edge the bed with steel, plastic or stone borders so rock stays put and stays out of the mower.
Frequently asked questions
How Much River Rock for a 20×20 bed?
A 20×20 bed at a 2 in depth needs about 3.6 tons of river rock (2.59 cubic yards).
How deep should river rock be?
2 inches for decorative cover, 3-4 inches where you want the rock to fully hide the soil and suppress weeds.
How much area does a ton of river rock cover?
Roughly 100-120 sq ft at 2 inches deep, or about half that at 4 inches. Larger stones pack less densely, so coverage varies a bit with size.
Is river rock better than mulch?
It costs more up front and holds heat around plants, but it never decomposes, so there is no annual top-up. Mulch is cheaper and better for planted beds; rock wins for borders, drainage paths and low-maintenance areas.
Do I need landscape fabric under river rock?
Almost always. Fabric keeps the rock from working down into the soil and slows weeds. Without it you will be topping up the bed within a few seasons.
Can river rock go against the house?
Yes - a rock strip along the foundation is common because it does not hold moisture against the wall the way mulch does. Keep the grade sloping away from the house and do not bury siding.