River Rock Calculator
Tons, cubic yards and bags of 1–3 inch, 2 inch, 3–5 inch and larger river rock, with the right depth for each stone size.
- Yards, tons, bags & cost
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River rock is smooth, rounded stone sorted by size – from 3/8″ pebbles up to 5–8″ cobbles – used for dry creek beds, drainage swales, borders, around foundations and anywhere you want a natural look that never needs replacing. Use this calculator to get tons, cubic yards and bags of river rock for your area, with the depth adjusted for the size of stone you choose.
How to use the river rock calculator
- Measure the area
Rectangles are easy; for a winding dry creek bed, measure its length along the centre line and its average width, and enter those. Use “Add another area” for separate beds.
- Set a depth that suits the stone size
The layer must be deep enough that the ground does not show through: roughly 1.5 to 2 times the largest stone. For 1–3″ rock use 3–4″; for 3–5″ rock use 5–6″. Small 3/8″–3/4″ pebbles only need 2″.
- Choose the rock size
Larger rock has more air between the stones, so a cubic yard weighs a little less. Pick the size you are actually buying for an accurate tonnage.
- Add a price
River rock is usually priced per ton in bulk and per 0.5 cu ft bag at garden centres. Enter either and the calculator totals it with delivery.
River rock formula
Cubic yards = Length (ft) × Width (ft) × Depth (in) ÷ 12 ÷ 27Tons = cubic yards × 1.35 (1–3″ river rock; use 1.3 for 3–5″, 1.2 for 5–8″)
Example: dry creek bed 30 ft long × 4 ft wide, 1–3″ rock, 4″ deep
- Area = 30 × 4 = 120 sq ft
- Volume = 120 × 4 ÷ 12 = 40 ft³ = 1.48 yd³
- Weight = 1.48 × 1.35 = 2.0 tons
- With 5% waste → order 2.1 tons
River rock sizes and where to use them
| Size | Typical name | Best for | Min. depth | Tons / yd³ |
|---|---|---|---|---|
| 3/8″ – 3/4″ | River pebbles, pea-size | Paths, planters, between pavers, pots | 2″ | 1.42 |
| 3/4″ – 1″ | Small river rock | Beds, borders, ground cover | 2–3″ | 1.40 |
| 1″ – 3″ | Medium river rock (most common) | Dry creek beds, drainage, foundation borders, xeriscaping | 3–4″ | 1.35 |
| 2″ | #2 river rock | Same uses, more uniform look | 3–4″ | 1.35 |
| 3″ – 5″ | Large river rock | Creek beds, swales, accent areas, erosion control | 5–6″ | 1.28 |
| 5″ – 8″ | Cobbles | Creek edges, retaining accents, water features | Single layer | 1.22 |
River rock coverage per ton
| Material | Density | Tons per yd³ | sq ft per ton at 2" | sq ft per ton at 3" | sq ft per ton at 4" | sq ft per ton at 6" |
|---|---|---|---|---|---|---|
| River rock 1"–3" | 100 lb/ft³ | 1.35 | 120 | 80 | 60 | 40 |
| River rock 2" (medium) | 100 lb/ft³ | 1.35 | 120 | 80 | 60 | 40 |
| River rock 3"–5" | 95 lb/ft³ | 1.28 | 126 | 84 | 63 | 42 |
| River rock 5"–8" (large) | 90 lb/ft³ | 1.22 | 133 | 89 | 67 | 44 |
| River pebbles 3/8"–3/4" | 105 lb/ft³ | 1.42 | 114 | 76 | 57 | 38 |
| Mexican beach pebbles | 105 lb/ft³ | 1.42 | 114 | 76 | 57 | 38 |
Coverage = 2,000 lb ÷ (density × depth in feet). Figures are for loose material; add 5–10% for waste and up to 20% for compacted base layers.
Planning a dry creek bed
A dry creek bed is the most common river rock project and the one where people most often under-order. Three things to build into your estimate:
- Dig it, don’t pile it. Excavate a shallow channel 4–8″ deep so the rock sits below grade and actually carries water. The rock volume is the channel volume plus a little for the banks.
- Mix sizes. A natural look uses mostly 1–3″ rock with 3–5″ rock along the edges and a few boulders as accents. Run the calculator twice – once for each size – using roughly 70% / 30% of the area.
- Fabric underneath. Non-woven landscape fabric stops the rock sinking into mud and lets water drain through. It also means the lower end of the depth range is enough.
How much does river rock cost?
River rock is priced higher than crushed stone because it is dredged, washed and screened rather than simply quarried. Bulk prices commonly fall between $45 and $130 per ton depending on size and colour, with Mexican beach pebbles and polished stone costing several times more. Bags (0.5 cu ft, around 40–50 lb) run $5–$12 each. Enter your local quote in the calculator; the difference between bulk and bagged is usually dramatic above half a cubic yard.
Frequently asked questions
How much does a yard of river rock weigh?
A cubic yard of 1–3″ river rock weighs about 2,700 lb (1.35 tons). Larger 3–5″ rock is a little lighter per yard (about 2,560 lb) because there is more air between the stones; small pebbles are a little heavier (about 2,830 lb).
How many square feet will a ton of river rock cover?
At 3 inches deep a ton of 1–3″ river rock covers about 80 sq ft; at 4 inches about 60 sq ft; at 2 inches about 120 sq ft.
How deep should river rock be?
Make the layer 1.5–2 times the largest stone size, and never less than 2 inches. For the common 1–3″ rock, 3–4 inches is right. For 3–5″ rock use 5–6 inches, and lay 5–8″ cobbles as a single layer.
How much river rock do I need for 100 square feet?
At 3 inches deep you need 25 cubic feet = 0.93 cubic yards, about 1.25 tons, or 50 bags of 0.5 cu ft. At 4 inches, 1.23 yards (1.7 tons).
Is river rock good for drainage?
Yes – the rounded stones leave plenty of space for water to move through, which is why river rock is used for dry creek beds, swales and downspout splash areas. For a buried French drain, however, washed crushed stone (#57) is normally used because it is cheaper and packs more firmly around the pipe.
River rock vs. pea gravel – which should I use?
Pea gravel (3/8″) is comfortable to walk on and suits patios and paths; river rock (1″ and up) is too lumpy underfoot but looks far more natural in beds and creek features and does not scatter as easily. Many landscapes use pea gravel for paths and river rock for the beds beside them.
