Calculators / River rock
Decorative, large stone
River rock calculator
Decorative beds, dry creek beds and borders. Larger stone means deeper layers and more weight per square foot than you expect.
How deep, by project
| Project | Depth | Notes |
|---|---|---|
| 3/4 to 1 in stone | 2–3 in | The most common decorative size. Two inches covers, three hides fabric properly. |
| 1 to 2 in stone | 3–4 in | Larger gaps need a deeper layer to stop light reaching the soil. |
| 2 to 4 in stone | 4–6 in | Usually placed rather than poured. Calculate volume, then expect to hand-set the top layer. |
| Dry creek bed | 4–6 in | Varying sizes, deepest in the channel centre. Add 20 percent over the calculated volume for the profile. |
| Foundation drainage strip | 3–4 in | Over fabric, sloped away from the wall. |
Stone size drives depth
This is the one material where the calculator's depth field needs thought before you type. A 2-inch layer of 1-inch stone covers the ground. A 2-inch layer of 2-inch stone is a single layer of rocks with soil showing between them.
The working rule is a depth of at least twice the nominal stone size. Rounding up here costs less than laying it twice.
Weight is the real constraint
River rock runs about 2,700 pounds per cubic yard. A modest 200 square foot bed at 3 inches is 1.85 cubic yards — two and a half tons of stone, moved one shovel at a time.
Plan the drop point carefully. Ask for it as close to the bed as the truck can safely tip, and hire or borrow a proper contractor wheelbarrow rather than the garden centre one.
It is permanent in a way mulch is not
Rock does not break down, so it never needs replacing — but it also never improves the soil, it radiates heat back at nearby plants, and removing it later is a genuinely miserable job. It suits borders, drainage runs and low-planting areas far better than mixed perennial beds.
Lay quality woven fabric first. Cheap spun fabric tears as the stone is raked and you end up with weeds growing through stone, which is far worse than weeds growing through mulch.
Common questions
How much river rock do I need?
Area in square feet times depth in feet, divided by 27, gives cubic yards. For 1-inch stone at 3 inches deep, one cubic yard covers about 108 square feet.
How much does a yard of river rock weigh?
Around 2,700 pounds, or 1.35 tons. Wet stone is heavier, and yards weigh the loaded truck, so rain adds a little to the bill.
How deep should river rock be?
At least twice the stone diameter. Two to three inches for 3/4-inch stone, four inches or more for 2-inch stone, otherwise the ground shows through.
Should I put fabric under river rock?
Yes, and use woven geotextile rather than lightweight weed cloth. Spun fabric tears while you are raking stone across it and then stops doing anything useful.
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