The core measurement
Area and depth determine volume
River rock coverage starts with the space the loose stone will fill. Multiply length by width for a simple bed, convert installed depth from inches to feet, then divide cubic feet by 27 to get cubic yards. Add your ordering allowance after calculating the installed volume. Convert yards to tons with the bulk weight for the actual product, which includes spaces between stones.
cubic yards = length (ft) × width (ft) × depth (in) ÷ 324For the 30 × 10 ft example at 3 in: 300 × 3 ÷ 324 = 2.78 yd³. Ten percent extra makes 3.06 yd³; multiply that by 1.35 short tons/yd³ for 4.13 short tons. The bag estimate divides the order volume in cubic feet by the volume printed on each bag and rounds up.
One cubic yard is 27 cubic feet. A US short ton is 2,000 pounds. Overage covers small measuring differences and uneven spreading; it is separate from the installed depth.
Coverage and stone choice
Choose depth for the look and job
Supplier labels such as “1–3 inch river rock” describe a mixed product, so a bag or sample matters more than a fixed depth rule. Smaller pebbles can cover a decorative bed at a thinner layer; larger stones may need more material to hide the soil between them. Rounded stone remains mobile underfoot, so a frequently walked path usually calls for a firmer surface such as angular aggregate or pavers. A rounded versus angular stone guide explains that tradeoff.
¾–1 in pebbles
For borders and decorative ground cover. Start the estimate near 2 in, then check a sample in place.
1–3 in river rock
For broad beds and visible drainage accents. Start near 3 in; large pieces and exposed fabric may call for more.
2–4 in stone
For bold edges and larger dry creek features. Start near 4 in for a volume estimate, then verify the finished look.
3–5 in cobbles
Often placed as larger individual pieces. A blanket depth estimate is rough; ask the yard about its actual size range.
River rock coverage at common depths
The table assumes 1.35 US short tons per cubic yard and excludes extra. Size alone does not set coverage; depth and the product's bulk weight do.
| Installed depth | 1 cubic yard covers | 1 short ton covers |
|---|---|---|
| 2 in | 162 sq ft | 120 sq ft |
| 3 in | 108 sq ft | 80 sq ft |
| 4 in | 81 sq ft | 60 sq ft |
| 5 in | 65 sq ft | 48 sq ft |
The 1.35 figure is a planning default. A supplier listing for 1–3 in river rock gives about 2,600 lb/yd³, illustrating why a local product value can differ. See Landscape Centre's river rock specifications and the site's bulk density guide.
Dry creek and swale projects
Measure the stone-lined surface, then assess the water
A dry creek's bottom and banks use more rock than its footprint suggests. Stretch a tape across the surface that will actually receive stone, following the slope from one upper edge, across the bottom, to the other edge. Multiply that developed width by the section length. If the creek narrows, widens, or changes depth, estimate those sections separately and add the quantities.
Identify the bottom, side slopes, bends, and where runoff will leave the feature.
Use the surface width that will receive stone, then enter its length and intended layer depth.
Where stormwater is concentrated or fast, channel capacity, stone size, gradation, and filter design need a site-specific assessment.
This calculator estimates quantity only. USDA NRCS stone sizing guidance considers flow and slope, while FHWA riprap guidance notes that angular stone generally performs best and that an underlying filter may be needed. See the site's dry creek bed guide and riprap calculator for related planning.
Before placing an order
Confirm the product and the finished surface
- Match the unit on the quote. Take both cubic yards and short tons to the stone yard, and ask for its actual loose bulk weight per yard.
- Check the grading in person. “River rock” can include very different shapes and size ranges, affecting the look and how comfortably it can be walked on.
- Read the bag volume. A 0.5 ft³ bag is only the calculator default; large landscape bags and pallet counts vary by product.
- Decide whether to use a separator. Permeable fabric can help keep soil and rock apart, but it is not a weed-free guarantee. Remove leaves and sediment as they accumulate. Around planting beds, stone can also increase summer heat near sensitive plants. University of Minnesota Extension describes these tradeoffs.
River rock calculator questions
How much river rock do I need for a 300-square-foot bed?
At 3 inches deep, 300 square feet takes 75 cubic feet, or 2.78 cubic yards, before extra. With 10% extra, order about 3.06 cubic yards. At an assumed 1.35 US short tons per cubic yard, that is about 4.13 tons. Confirm the bulk weight with your supplier.
How many square feet does one ton of river rock cover?
Using the calculator default of 1.35 short tons per cubic yard, one ton covers about 120 square feet at 2 inches, 80 square feet at 3 inches, or 60 square feet at 4 inches. These are volume-based estimates before any extra to order.
Does the size of the stone change the calculation?
Stone size affects the depth you choose and can change bulk weight per cubic yard. The calculator does not infer either from the trade name: choose a depth that covers your surface and enter the supplier weight when you have it.
Can I use this calculator for a dry creek bed?
Yes, for estimating material volume. Measure the length and the stone-lined width across the bottom and both banks, then calculate each section separately if the width or depth changes. The result does not determine channel capacity or rock stability in flowing water.
Will fabric under river rock stop weeds?
A permeable separator can reduce soil and stone mixing, but seeds and organic debris can collect above it and grow weeds. Keep leaves out of the rock, plan for maintenance, and consider heat around sensitive plants.