What to measure
How to use the river rock calculator
Choose a rectangle or circle, enter the bed size and the depth of rock. For long, curving borders, measure the length along the middle and the average width.
The formula
- Cubic yards = length × width × depth (all in feet) ÷ 27
- Tons = cubic yards × 1.35
- Bags = cubic feet ÷ 0.5
Worked example: 10 × 10 ft bed, 2 in deep
- 10 × 10 × (2 ÷ 12) = 16.67 cu ft = 0.62 cubic yards
- 0.62 × 1.35 = 0.83 tons
- Or 16.67 ÷ 0.5 → 34 bags
River rock by bed size
| Bed | Depth | Tons | 0.5 cu ft bags |
|---|---|---|---|
| 3 × 20 ft border | 2 in | 0.5 | 20 |
| 3 × 20 ft border | 3 in | 0.75 | 30 |
| 4 × 25 ft bed | 3 in | 1.25 | 50 |
| 10 × 10 ft bed | 3 in | 1.25 | 50 |
| 10 × 10 ft bed | 4 in | 1.67 | 67 |
| 5 × 30 ft bed | 4 in | 2.5 | 100 |
| 6 ft circle around a tree | 2 in | 0.24 | 10 |
Common mistakes
- Picking the depth before the stone size. Larger stones need a deeper layer to cover the fabric, so choose the rock first and set the depth from it.
- Measuring a curved border on its outside edge. That overstates the area. Measure along the middle and use the average width.
- Forgetting the weight. A ton of rock is more than most pickups should carry in one trip; check your payload or arrange delivery.
- Laying rock on bare soil. Without fabric the stones sink and weeds grow through, and you end up topping the bed up.
Frequently asked questions
How deep should river rock be?
About twice the size of the stones — 2 inches for ¾–1 in rock, 3–4 inches for 1½–3 in rock. Too thin and the fabric shows; too deep wastes stone.
How much does a yard of river rock weigh?
About 1.35 tons (2,700 lb) per cubic yard. Larger stones leave more air between them, so weight varies.
How many bags of river rock do I need?
A 10 × 10 ft bed 2 in deep needs about 34 bags of 0.5 cu ft. Bags make sense for small beds; for more than half a yard, bulk is cheaper.
Do I need landscape fabric under river rock?
It's recommended. Fabric keeps rock from sinking into the soil and slows weeds, while still letting water through.
How much river rock for a 3 ft wide border?
A 3 × 20 ft border needs 0.37 cubic yards (about 0.5 tons or 20 bags) at 2 inches deep, and 0.56 cubic yards (0.75 tons or 30 bags) at 3 inches.
How many bags of river rock to go around a tree?
A 6 ft circle 2 inches deep holds about 4.71 cu ft, so 10 bags of 0.5 cu ft. The trunk takes up a little of that space, so the count is slightly generous.
How much river rock for a dry creek bed?
Treat it as a long rectangle using the average width. A 3 × 40 ft channel lined 4 inches deep needs 1.48 cubic yards, about 2 tons or 80 bags.
Can I use the gravel calculator for river rock?
Yes. The gravel calculator has River rock in its material list at the same 1.35 tons per cubic yard, so both give the same tons. This page adds the bag count.
Sources
Formulas and defaults last reviewed October 30, 2026. How we check our math.