How to use the river rock calculator
- Choose the shape. Rectangle, circle, several parts for L-shapes and curves, or type in the area if you already know it.
- Enter the size and depth. Length and width in feet; depth in inches. Feet and inches like 12' 6" work too.
- Read the result in cubic yards, tons and bags. Under Adjust assumptions you can change the weight per yard, extra and bag size.
- Add your supplier's price per ton, yard or bag to see the cost, including delivery.
The river rock formula
Cubic feet = area (sq ft) × depth (in) ÷ 12
Cubic yards = cubic feet × (1 + extra) ÷ 27
Tons = cubic yards × weight per cubic yard
Bags = cubic feet with extra ÷ bag size, rounded up
Worked example
A 20 × 4 ft border, 3 inches deep
- 80 sq ft × 0.25 = 20 cu ft; with 5% = 21 cu ft.
- 21 ÷ 27 = 0.78 cubic yards.
- At about 1.35 tons per yard: 1.05 tons, or 42 bags of 0.5 cu ft.
How far a cubic yard goes
| Depth | One cubic yard covers | 0.5 cu ft bags per 10 sq ft |
|---|---|---|
| 1 in | 324 sq ft | 1.7 |
| 2 in | 162 sq ft | 3.3 |
| 3 in | 108 sq ft | 5.0 |
| 4 in | 81 sq ft | 6.7 |
| 6 in | 54 sq ft | 10.0 |
A cubic yard is 27 cubic feet, or 54 bags of 0.5 cu ft.
River rock sizes
- 3/4 to 1 in: paths and small beds, 2 in deep.
- 1 1/2 to 2 in: beds and borders, 3 in deep.
- 3 to 5 in: dry creek beds and drainage, 4 to 6 in deep.
Common mistakes to avoid
- Too shallow. Thin layers show soil and fabric between stones.
- Skipping edging. Rock spreads into the lawn and mower without a border.
- Rock against the foundation without drainage. Rock beds should slope away from the house.
- Ordering by volume, priced by weight. Confirm whether the price is per ton or per yard.
Frequently asked questions
How deep should river rock be?
About 2 inches for small stones (3/4 to 1 1/2 in) and 3 to 4 inches for larger rock (1 1/2 to 3 in). The layer should be about twice as deep as the stone size.
How much area does a ton of river rock cover?
At 1.35 tons per yard, a ton is about 0.74 cubic yards: about 120 sq ft at 2 inches or 80 sq ft at 3 inches.
Should I put landscape fabric under river rock?
Usually yes. Fabric keeps rock from sinking into the soil and slows weeds, though some weeds will root in debris on top.
Is river rock sold by the ton or the yard?
Most landscape suppliers sell rock by the ton; some sell by the yard. The calculator gives both.
How much does a bag of river rock cover?
A 0.5 cu ft bag covers about 2 sq ft at 3 inches deep, or 3 sq ft at 2 inches.