River Rock Calculator
Decorative river rock for beds, borders, dry creeks and drainage. The rule is depth ≈ 1.5 × the largest stone: 2″ for ¾–1″ rock, 3″ for 1–3″, 4″ for 3–5″ cobbles. Lay it over landscape fabric so it does not sink into the soil.
Order 1.25 t — sold by the ton bulk; decorative rock often comes in 1-ton super sacks.
- Area
- 80 ft²
- Volume (20.0 ft³)
- 0.74 yd³
- Net weight @ 1.35 t/yd³
- 2,000 lb · 1.00 t
- Waste / settling 5%
- + 0.05 t
- Order quantity
- 1.05 tons
- Truckloads
- 1 × tri-axle dump (≈20 t)
- Metric
- 0.57 m³ · 0.95 tonnes
- 50 lb bag (0.5 ft³)
- 42 bags
- Materials + delivery$80–$200 / ton · Sep 2026
- $190 – $340
- Installed (with labor)typ. $305
- $222 – $424
Quantities follow the ticket. Links may earn us a commission at no cost to you; they never change a number.
What will this river rock job cost?
See the installed price range for these quantities and get up to 3 quotes from local contractors. Free, no obligation.
Common bed sizes, answered
- How Much River Rock for a 4×8 Bed?32 ft²
- How Much River Rock for a 5×10 Bed?50 ft²
- How Much River Rock for a 10×3 Bed?30 ft²
- How Much River Rock for a 10×10 Bed?100 ft²
- How Much River Rock for a 12×4 Bed?48 ft²
- How Much River Rock for a 15×4 Bed?60 ft²
- How Much River Rock for a 20×3 Bed?60 ft²
- How Much River Rock for a 20×4 Bed?80 ft²
- How Much River Rock for a 20×10 Bed?200 ft²
- How Much River Rock for a 30×4 Bed?120 ft²
- How Much River Rock for a 40×3 Bed?120 ft²
- How Much River Rock for a 50×4 Bed?200 ft²
How to calculate river rock by hand
Tons = Length (ft) × Width (ft) × Depth (in) ÷ 12 ÷ 27 × 1.35 t/yd³
Worked example
- Area: 20 ft × 4 ft = 80 ft².
- Volume: 80 ft² × (3 in ÷ 12) = 20 ft³ = 0.74 yd³.
- Weight: 0.74 yd³ × 1.35 t/yd³ = 1.0 ton.
- Waste 5%: 1.0 × 1.05 = 1.05 tons → order 1.25 tons.
- Bagged: 21 ft³ ÷ 0.5 ft³ = 42 × 50 lb bags.
- 1 ton of 1–3″ rock at 3″
- ≈ 80 ft²
- 1 ton of ¾–1″ rock at 2″
- ≈ 115 ft²
- 1 yd³ river rock
- ≈ 2,700 lb · 1.35 t
- Depth rule
- 1.5 × largest stone
Questions crews ask
How much river rock do I need?
Square feet × depth in inches ÷ 324 gives cubic yards; × 1.35 gives tons. A 20 × 4 ft border at 3″ needs 0.74 yd³, about 1 ton, or 42 × 50 lb bags. Order 1.25 tons bulk.
How deep should river rock be?
About 1.5 times the largest stone so the fabric never shows: 2″ for ¾–1″ rock, 3″ for 1–3″, 4″ for 3–5″ cobbles. Deeper wastes money and makes beds hard to weed; shallower shows fabric within a season.
How much does a ton of river rock cover?
Roughly 80 ft² at 3″ deep, 115 ft² at 2″, and 60 ft² at 4″. Larger stone leaves more voids, so 3–5″ cobbles cover slightly more per ton than the calculator’s 1–3″ default.
How many bags of river rock are in a ton?
About 40 × 50 lb bags. Bagged river rock is $5–$10 per bag ($200–$400 per ton), so bulk at $80–$200 per ton plus delivery is cheaper above roughly half a ton.
Do I need landscape fabric under river rock?
Yes, unless it is a drainage application. Fabric keeps the rock from working into the soil and cuts weeding by most of the way. For dry creek beds use fabric and a 1″ layer of pea gravel under the cobbles.