Bags of River Rock for a 16x20 Patio
How many bags of river rock for a 16x20 patio: at 3 inches deep you need about 80.0 cubic feet, which is 160 bags of the common 0.5 cubic foot size. If your store sells river rock in 50-pound bags instead, figure about 160 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 | 26.7 | 54 | 54 |
| 2 in | 53.3 | 107 | 107 |
| 3 in | 80.0 | 160 | 160 |
| 4 in | 106.7 | 214 | 214 |
How to figure it
- Area: 16 × 20 = 320 sq ft.
- Volume: 320 × (3 ÷ 12) = 80.0 cu ft.
- Bags: 80.0 ÷ 0.5 = 160 bags (round up).
Bags or bulk?
A cubic yard is 27 cubic feet, so 80.0 cubic feet is 2.96 yards, about 4.0 tons. At this size, a bulk delivery usually beats a cart full of bags once you count trips. Compare the bag price × 160 against a bulk quote for 4.4 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.
Install tips for a patio
- 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.
Where river rock fits
Good uses:
- 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 2 inches takes about 2.4 tons.
- Weight used here: about 1.35 tons per cubic yard.
Where estimates go wrong
- Assuming every supplier uses the same weight. Two yards selling the same product name can quote different tons per yard.
- Mixing up cubic yards and tons. Yards are volume, tons are weight; convert with the product’s weight per yard.
- Skipping drainage. Water sitting under any surface softens the base and leads to ruts and potholes.
- Using inches as if they were feet. Depth has to be divided by 12 before you multiply; skipping that step inflates the order twelvefold.
Questions people ask
How many bags of river rock for a 16x20 patio?
About 160 bags of 0.5 cubic feet at 3 inches deep.
How many 50 lb bags of river rock for 16x20?
About 160 bags at 3 inches.
How many 0.5 cubic foot bags are in a cubic yard?
54 bags.
How many cubic feet is a 16x20 patio at 3 inches?
About 80.0 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 16x16 Patio
- Bags of River Rock for a 16x18 Patio
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