River Rock Calculator
Punch in your area and depth, pick the stone size — cubic yards, tons, and a coverage estimate come back adjusted for how rounded rock actually fills space.
Estimate the exact tonnage and volume of river rock, pea gravel, or crushed stone needed to complete your landscaping project efficiently.
River rock looks deceptively lightweight at the supplier’s yard. A cubic yard of it — roughly the bed of a full-size pickup — weighs between 2,500 and 2,700 pounds depending on stone size. Underestimate and you’re making a second trip; overestimate and you’re moving surplus by hand. The river rock calculator above converts your project dimensions directly into cubic yards and tons, with coverage adjusted for stone size, so the number you call in to the yard is the number you actually need.
Why Stone Size Changes the Calculation
Unlike crushed gravel, which compacts and locks together, river rock is rounded — every stone leaves void space around it. Larger stones leave more air between them, which means a given depth of large cobble covers less usable area per ton than smaller 1-inch stones. Ordering by volume (cubic yards) sidesteps this issue; ordering by weight (tons) requires knowing which size you’re buying.
| Stone Size | Approx. Weight per Cubic Yard | Coverage per Ton at 2″ Depth | Coverage per Ton at 3″ Depth |
|---|---|---|---|
| ¾”–1″ (small) | ~2,700 lb (1.35 tons) | ~90–100 sq ft | ~60–65 sq ft |
| 1″–2″ (medium) | ~2,600 lb (1.30 tons) | ~80–90 sq ft | ~55–60 sq ft |
| 2″–3″ (large) | ~2,500 lb (1.25 tons) | ~70–80 sq ft | ~50–55 sq ft |
| 3″–5″ cobble | ~2,410 lb (1.21 tons) | ~60–70 sq ft | ~45–50 sq ft |
| 5″–8″ cobble | ~2,350 lb (1.18 tons) | Single layer only | Single layer only |
Recommended Depth by Application
| Application | Recommended Depth | Notes |
|---|---|---|
| Decorative garden beds | 2–3 inches | Enough to cover landscape fabric and suppress weeds |
| Pathways and walkways | 3–4 inches | Deeper prevents stones pushing into soil underfoot |
| Tree rings and borders | 2 inches | Keep rock 3–4 inches from trunk to prevent rot |
| Dry creek bed (decorative) | 4–6 inches | Mix sizes — larger stones in center, medium at edges |
| Drainage swale (functional) | 6 inches minimum | Use washed stone; non-woven geotextile fabric underneath |
| Erosion control on slopes | 4–6 inches | Larger cobble (3–5″) needed for any slope carrying runoff |
Quick Tonnage Reference for Common Project Sizes
Based on 1–2″ river rock at 1.3 tons/yd³, including 10% waste.
| Area | 2″ Depth | 3″ Depth | 4″ Depth |
|---|---|---|---|
| 50 sq ft | 0.5 tons | 0.8 tons | 1.1 tons |
| 100 sq ft | 1.0 ton | 1.5 tons | 2.1 tons |
| 200 sq ft | 2.1 tons | 3.1 tons | 4.1 tons |
| 400 sq ft | 4.1 tons | 6.2 tons | 8.2 tons |
| 600 sq ft | 6.2 tons | 9.2 tons | 12.3 tons |
Landscape Fabric: Don’t Skip It
River rock settled directly onto soil is a long-term maintenance problem. Rounded stones migrate into soft ground, soil works up between them over time, and weeds establish in the gaps within one or two seasons. Woven landscape fabric (not plastic sheeting — it blocks water) laid before the rock prevents this. Use fabric staples every 12–18 inches and overlap seams by 6 inches. Budget the fabric before calculating rock depth — the fabric adds negligible thickness but the labor of removing and re-laying rock because weeds took hold costs far more than the fabric itself.
Edging: Why Rounded Rock Needs It More Than Other Materials
Crushed gravel and decomposed granite interlock and hold a reasonably stable edge. River rock doesn’t — it rolls. Without edging along beds, pathways, and lawn borders, rounded stones migrate outward and thin the coverage across the center. Metal edging, plastic edging, or stone borders installed before the rock arrives solves this permanently. Installing edging after spreading rock means moving it out of the way first.
Bags vs. Bulk: When Each Makes Sense
Bagged river rock (typically 0.5 cubic feet per bag) is convenient for small accent areas, tree rings, and tight spaces where a delivery truck can’t reach. For anything over 1 ton — roughly a 100 sq ft bed at 3 inches deep — bulk delivery almost always costs less per ton and saves the labor of carrying and cutting dozens of bags. A pallet of 50-pound bags covers roughly 40–50 sq ft at 3 inches; one bulk ton covers 55–65 sq ft at the same depth, at typically half the per-unit cost.
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Standard river rock weighs approximately 2,500–2,700 pounds (1.25–1.35 tons) per cubic yard depending on stone size. Smaller stones pack tighter and weigh more per cubic yard; larger cobble leaves more void space and weighs less. Your supplier can confirm the exact density for the specific product they stock — this matters most for large orders where a small density difference adds up to significant tonnage.
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Yes, with the right installation. Washed river rock works well in drainage swales, French drains, and dry creek beds because water moves freely through the void spaces between rounded stones. Use non-woven geotextile fabric underneath to prevent soil migration into the rock layer over time. For functional drainage swales carrying runoff, a minimum 6-inch depth with a safe outlet is recommended — decorative creek beds are typically shallower.
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Both are rounded, naturally smoothed stones, but pea gravel is smaller (¼"–½") and more uniform in size. River rock is larger (¾" and up) and more varied in size and color. Pea gravel is softer underfoot for pathways and playgrounds. River rock is better for drainage features, dry creek beds, and slopes.
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In most applications, yes. Without fabric, river rock works into the soil over time, weeds establish in the gaps, and the bed requires full replacement within a couple of seasons. Use woven landscape fabric, overlap seams by 6 inches, and stake it down before placing rock. The exception is functional drainage features — use non-woven geotextile designed for drainage instead.