River rock calculator for Montana
Stone size changes coverage: 3-inch rock covers about half the area per ton as 1-inch rock.
Enter your project dimensions
River rock coverage depends on the stone size. To cover the ground, plan a layer about double the stone diameter: use 2 inches for 1-inch rock and 4 inches or more for 3-inch rock. The same ton then covers half as much area. Choose the size and enter the bed dimensions in this calculator to get tonnage using river rock's 2,700 lb per cubic yard weight. The delivered pile can appear smaller than expected, since a ton is about three quarters of a cubic yard. If fabric shows after spreading, the issue is usually insufficient depth rather than the amount ordered.
Planning your order
- Record every border and bed in feet, then let multiple-areas mode add the separate spaces together.
- Use a layer about twice the stone diameter: 2 inches with 3/4 to 1 inch rock, 3 to 4 inches with 1 to 3 inch rock, and 4 to 5 inches for larger pieces.
- Divide cubic feet by 27 to find cubic yards, then multiply yards by 1.35 to calculate tons.
Per-ton coverage by stone size
| Stone size | Layer depth | 1 ton covers |
|---|---|---|
| 3/4–1" river rock | 2 inches | ≈ 120 sq ft |
| 1–3" river rock | 3 inches | ≈ 80 sq ft |
| Large river rock (2–4") | 4–5 inches | ≈ 53 sq ft |
| Oversize accents | single layer | 35–50 sq ft |
| Project | Typical size | Depth | Volume | Weight |
|---|---|---|---|---|
| Foundation border | 40 x 3 ft | 3" | 1.1 yd³ | 1.5 tons |
| Dry creek bed | 25 x 4 ft | 4" | 1.2 yd³ | 1.7 tons |
| Accent beds | ≈ 150 sq ft | 2" | 0.9 yd³ | 1.3 tons |
| Downspout splash zones, x4 | 3 x 2 ft each | 3" | 0.2 yd³ | 0.3 tons |
| Front-yard xeriscape | ≈ 600 sq ft | 3" | 5.6 yd³ | 7.5 tons |
Install fabric before adding rock
Bare soil lets stone work downward over time, while weeds come up through the gaps. Without fabric, a bed can need more rock after three years, even though a roll of fabric costs only a few dollars. Put down non-woven fabric, secure it with pins, and spread the rock over it. For drain rock in a working drainage path, wrap the fabric around the stone instead of laying it beneath the rock.
Ways to create a natural rock bed
- Use a 1 to 2 inch base and group larger stones through it. All one size can give the bed a parking-lot-median look.
- For a dry creek bed, sink the largest anchor stones a third of their depth to make them appear water-set.
- Hose the rock after it is spread. Dust on delivered material can dull the color until it is rinsed away.
- At a foundation, place 3 to 4 inches over fabric and slope the bed slightly from the wall. This gives it a finished appearance while carrying roof water along the bed.
- Use a blower on low to remove leaves. A rake can send rock into the grass, where mower blades can hit it later.
Example: a 200-square-foot bed
At 2 inches deep, one-inch river rock works out as 200 x 0.167 = 33 cubic feet = 1.2 cubic yards, or about 1.7 tons. Order two tons. Put the extra along the front edge in a double layer, since that visible area thins first.
Rock or mulch over five years
Mulch costs less per delivery and feeds the soil, but it needs replacing every year or two. River rock has a higher initial cost and generally keeps the same look into year five. Rock also heats nearby soil in summer, so mulch usually belongs in planted beds while rock works for borders, drainage lines, and edges. Enter the same dimensions in both calculators to see how the tonnage drives the price difference.
River rock coverage and pricing FAQs
How can I calculate the river rock I need?
What area does 1 ton of river rock cover?
What will 50 lbs of river rock cover?
What is the cost of a ton of river rock?
What depth is needed for river rock?
Is landscape fabric needed under river rock?
Can river rock be installed over mulch?
What does a yard of river rock weigh?
Other calculators
Rock beds need less frequent replacement.
River rock, large river rock, and drain rock sold by the ton with free delivery included.
