Bags of River Rock for a 4x20 Walkway
How many bags of river rock for a 4x20 walkway: at 3 inches deep you need about 20.0 cubic feet, which is 40 bags of the common 0.5 cubic foot size. If your store sells river rock in 50-pound bags instead, figure about 40 bags, since river rock weighs roughly 100 pounds per cubic foot.
Volume and tonnage calculator →Bag count by depth
| Depth | Cubic feet | 0.5 cu ft bags | 50 lb bags (approx.) |
|---|---|---|---|
| 1 in | 6.7 | 14 | 14 |
| 2 in | 13.3 | 27 | 27 |
| 3 in | 20.0 | 40 | 40 |
| 4 in | 26.7 | 54 | 54 |
How to figure it
- Area: 4 × 20 = 80 sq ft.
- Volume: 80 × (3 ÷ 12) = 20.0 cu ft.
- Bags: 20.0 ÷ 0.5 = 40 bags (round up).
Bags or bulk?
A cubic yard is 27 cubic feet, so 20.0 cubic feet is 0.74 yards, about 1.0 tons. Under a yard, bags save a delivery fee and are easy to haul in a car or pickup. Compare the bag price × 40 against a bulk quote for 1.1 tons delivered.
About river rock
River rock is smooth, water-worn stone sold in sizes from about 3/4 inch to several inches. Larger sizes cover fewer square feet per ton at the same depth because the voids between stones are bigger.
Before you spread for a walkway
- Dig and level. Remove sod and set the base slightly below the surrounding grade.
- Edge it. Steel, plastic or stone edging keeps material in place.
- Spread in layers. Rake to depth, then rake smooth; rounded stone will not compact.
- Buy a few extra. Grab 5 to 10 percent more bags for settling and touch-ups.
The volume and tonnage calculator handles other sizes and depths.
Good and poor uses for river rock
Works well for:
- Dry creek beds and drainage swales
- Decorative borders and planting beds
- Around downspouts to stop splash erosion
Less suited to:
- Walking surfaces
- Driveways
- Bases under slabs or pavers
Quick reference numbers
- Per inch over 100 sq ft: about 0.42 tons of river rock (0.31 cubic yards).
- Per inch over 1,000 sq ft: about 4.2 tons.
- Another size for comparison: a 12x24 area at 3 inches takes about 3.6 tons.
- Weight used here: about 1.35 tons per cubic yard.
Where estimates go wrong
- Mixing up cubic yards and tons. Yards are volume, tons are weight; convert with the product’s weight per yard.
- Ignoring the base. A thin surface layer over soft soil fails early no matter how much material is on top.
- Skipping drainage. Water sitting under any surface softens the base and leads to ruts and potholes.
- Assuming every supplier uses the same weight. Two yards selling the same product name can quote different tons per yard.
Questions people ask
How many bags of river rock for a 4x20 walkway?
About 40 bags of 0.5 cubic feet at 3 inches deep.
How many 50 lb bags of river rock for 4x20?
About 40 bags at 3 inches.
How many 0.5 cubic foot bags are in a cubic yard?
54 bags.
How many cubic feet is a 4x20 walkway at 3 inches?
About 20.0 cubic feet.
When does bulk make more sense?
Usually once the job passes about a cubic yard, or when you would need more than a few car trips.
Related guides
- How Much Does a Ton of River Rock Cover?
- Tons to Cubic Yards for Gravel: Conversion Chart
- How Much Does a Ton of Gravel Cover? Depth Chart
- Bags of River Rock for a 4x10 Walkway
- Bags of River Rock for a 4x15 Walkway
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