River Rock Calculator
Find the tons of river rock needed for beds, dry creeks and drainage.
What you'll need to order
- river rock
- landscape fabric
- steel or stone edging
Prices vary by region and haul distance. Get quotes from at least two local suppliers.
How this calculator works
tons = length × width × (depth ÷ 12) × 105 ÷ 2000
River rock weighs about 105 lb per cubic foot, roughly 2,835 lb per cubic yard. Larger stone sizes leave bigger voids and cover slightly more area per ton than the figures here suggest.
Switch the site to metric — the control is in the footer — and your inputs, your results and the tables below follow. The formula, the constants, the guidance text and the sources stay in US units on purpose: that is how the standards they come from are written, and restating them would detach each figure from the document you are meant to be able to check it against.
Where these numbers come from
- ASTM C29/C29M 2023 — the test method that defines bulk density for river rock; the figure used here is a typical published value, not a mandated one
Check the edition. Codes are amended every few years, and the one your inspector works from may not be the one named above.
Worked example
With length 10 ft, width 10 ft, depth 3 in, this calculator returns 1.31 tons.
River rock coverage by depth
Figures below assume length 10 ft × width 10 ft. Each row is a link that fills in the calculator above. Send one and the other end sees the same figures you do.
| Depth | River rock needed (tons) | Volume (cu yd) |
|---|---|---|
| 1 in | 0.44 | 0.31 |
| 2 in | 0.87 | 0.62 |
| 3 in | 1.31 | 0.93 |
| 4 in | 1.75 | 1.23 |
| 6 in | 2.63 | 1.85 |
Per 100 square feet. River rock does not compact, so the depth you spread is the depth you keep.
How much river rock for a bed, path or dry creek?
Every row here opens the calculator already filled in. Copy that link and the numbers travel with it.
| Job | Size | River rock needed | Material cost |
|---|---|---|---|
| Tree ring | 6 ft × 6 ft × 3 in | 0.47 tons | $21 – $71 |
| Foundation border | 40 ft × 3 ft × 3 in | 1.57 tons | $71 – $236 |
| Dry creek bed deeper, to look natural |
30 ft × 4 ft × 6 in | 3.15 tons | $142 – $473 |
| Downspout splash area | 8 ft × 4 ft × 4 in | 0.56 tons | $25 – $84 |
| Large decorative bed | 40 ft × 12 ft × 3 in | 6.30 tons | $284 – $945 |
Rounded stone migrates without edging. Budget for steel or stone edging on anything bordering a lawn.
Cost range uses $45–$150 per ton for material only.
What does river rock cost?
Material typically runs $45 to $150 per ton. Delivered, not spread. Larger and more uniformly graded stone costs considerably more.
What moves the price:
- Stone size — 1 to 2 in is cheapest, 3 to 5 in accent stone costs two to three times more
- Colour consistency, which is what separates budget from premium river rock
- Haul distance, often the largest single line on a small order
- Whether the product is washed
Prices are US averages and move with fuel, season and haul distance. Always get two local quotes before budgeting.
River rock sizes and where they work
| Type | Stone size (in) | Notes |
|---|---|---|
| Pea size | 0.50 | Paths and playgrounds; moves underfoot |
| Small river rock | 1.50 | The general-purpose landscape size |
| Medium river rock | 3.00 | Dry creek beds, drainage swales |
| Large river rock | 5.00 | Accent stone, erosion control on slopes |
| Boulder grade | 12.00 | Sold by the piece, not by the ton |
Bigger stone means fewer pieces per ton and more visible gaps. Below about 2 inches, expect the stone to work its way into the soil without fabric beneath it.
Frequently asked questions
How many tons of river rock per square foot?
About 0.026 tons per square foot at 3 inches deep, so 100 sq ft needs roughly 2.6 tons. Halve it at 1.5 inches, double it at 6.
Is river rock cheaper than mulch?
It costs several times more upfront but never needs replacing. Over ten years river rock usually works out cheaper than mulch topped up annually — the trade-off is that it adds nothing to the soil.
Does river rock get hot?
Yes, noticeably. Stone stores heat and radiates it back, which is why it is a poor choice against a south-facing wall or around heat-sensitive plants in hot climates.
How much river rock do I need?
Multiply your area in square feet by the depth in feet, then multiply by 105 and divide by 2,000 for tons. A 25 by 6 ft bed at 3 inches deep needs about 2 tons.
How much area does a ton of river rock cover?
At 2 inches deep, about 114 square feet. At 3 inches, roughly 76 square feet. At 4 inches, around 57 square feet. Larger stone covers a little more because of the void space between pieces.
How deep should river rock be in a landscape bed?
Two to three inches over landscape fabric is enough to suppress weeds and stay put. Going deeper wastes stone and makes planting harder. Dry creek beds are the exception and want 4 to 6 inches.
What size river rock should I use?
For beds and ground cover, 1 to 2 inch stone is the usual choice — small enough to look even, large enough not to scatter. Dry creek beds mix 2 to 5 inch stone for a natural look. Anything under 1 inch behaves like pea gravel and migrates.
Do I need landscape fabric under river rock?
Yes, in planting beds. Without it the stone works its way into the soil within a couple of seasons and weeds push straight through. Use a woven fabric rather than the thin non-woven type, which tears under stone.