How Much River Rock for a 4×8 Bed?
A 4 × 8 ft bed (32 ft²) at 3″ deep needs 0.4 tons of river rock — 0.30 yd³ net plus 5% waste. Order 0.50 t — sold by the ton bulk; decorative rock often comes in 1-ton super sacks.
4×8 at other depths
| Depth | Volume | Order (tons) | 50 lb bag (0.5 ft³) |
|---|---|---|---|
| 2″ | 0.20 yd³ | 0.3 tons | 12 |
| 3″ (this page) | 0.30 yd³ | 0.4 tons | 17 |
| 4″ | 0.40 yd³ | 0.6 tons | 23 |
Other bed sizes
Order 0.50 t — sold by the ton bulk; decorative rock often comes in 1-ton super sacks.
- Area
- 32 ft²
- Volume (8.0 ft³)
- 0.30 yd³
- Net weight @ 1.35 t/yd³
- 800 lb · 0.40 t
- Waste / settling 5%
- + 0.02 t
- Order quantity
- 0.42 tons
- Truckloads
- 1 × tri-axle dump (≈20 t)
- Metric
- 0.23 m³ · 0.38 tonnes
- 50 lb bag (0.5 ft³)
- 17 bags
- Materials + delivery$80–$200 / ton · Sep 2026
- $130 – $190
- Installed (with labor)typ. $176
- $143 – $224
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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.
Different size or depth?
Open the full river rock calculator to change every input, pick a material and see truckloads.
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.