Free River Rock Calculator
Use this river rock calculator to see how much river rock or landscape rock to buy for your beds and borders.
River rock is rounded, smooth stone sold in sizes from about 3/4 inch to 3 inches or more. The right depth depends on the stone size: the layer should be at least as deep as the larger stones, so the ground does not show through.
It is heavier than it looks, at roughly 1.4 tons per cubic yard, so small orders are usually bagged and larger ones delivered.
River rock example: a garden border
A 20 ft long, 3 ft wide border at 3 in deep: 60 sq ft × 3 in ÷ 12 = 15 cu ft, plus 10% extra = 16.5 cu ft. Divide by 27 to get 0.61 cubic yards, which weighs about 0.86 tons, or 33 × 0.5 cu ft bags.
How deep should river rock be?
| Use | Depth | Notes |
|---|---|---|
| Small stone (3/4 to 1.5 in) | 2 in | |
| Medium stone (1 to 3 in) | 3 in | |
| Large stone (3 to 5 in) | 4 to 5 in | |
| Dry creek bed | 4 to 6 in | Mix sizes and add larger boulders on top. |
Coverage per cubic yard and per bag
| Depth | Sq ft per cubic yard | Sq ft per 0.5 cu ft bag |
|---|---|---|
| 1 in | 324 | 6 |
| 2 in | 162 | 3 |
| 3 in | 108 | 2 |
| 4 in | 81 | 1.5 |
Buying tips
- Lay landscape fabric first. River rock is hard to clean if weeds grow up through it.
- Unlike mulch, rock does not break down, so you only buy it once. Spending on edging and fabric is worth it.
- Decorative rock varies a lot in price by colour and source. Enter your supplier's price per ton or yard to see the total.
How much does river rock weigh?
A cubic yard of river rock typically weighs 2,600 to 3,000 lb (1.3 to 1.5 tons). The calculator uses 2,800 lb (1.4 tons) per cubic yard. Moisture and grading change the weight, so if your supplier sells by the ton, ask for their figure.
Frequently asked questions
How much river rock do I need per square foot?
At 3 inches deep, each square foot needs 0.25 cu ft. One cubic yard covers about 108 sq ft at that depth.
How much does a ton of river rock cover?
About 115 sq ft at 2 inches deep or about 77 sq ft at 3 inches, at a typical 1.4 tons per cubic yard.
Is river rock better than mulch?
Rock lasts for years and does not blow away, but it gets hot in sun and does not feed the soil. Mulch is better around plants that like rich, cool soil.
How accurate is this river rock calculator?
The river rock calculator gives the exact volume for the measurements you enter, then adds 10% extra (you can change it). Weights use a typical 1.4 tons per cubic yard; real loads vary with moisture, so confirm with your supplier if you buy by the ton. Measure carefully: an error of one inch in depth changes a 3 inch layer by a third.
How the river rock calculator works
Volume = area × depth. Each area is worked out from its shape (length × width, π × radius², or ½ × base × height), converted to square feet, multiplied by the depth in feet, and added up. Cubic feet ÷ 27 = cubic yards.The extra percentage is then added, and bag counts are rounded up to whole bags. See how we calculate for every figure we use.