Bags of River Rock for a 20x20 Patio

How many bags of river rock for a 20x20 patio: at 3 inches deep you need about 100.0 cubic feet, which is 200 bags of the common 0.5 cubic foot size. If your store sells river rock in 50-pound bags instead, figure about 200 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	33.3	67	67
2 in	66.7	134	134
3 in	100.0	200	200
4 in	133.3	267	267

How to figure it

Area: 20 × 20 = 400 sq ft.
Volume: 400 × (3 ÷ 12) = 100.0 cu ft.
Bags: 100.0 ÷ 0.5 = 200 bags (round up).

Bags or bulk?

A cubic yard is 27 cubic feet, so 100.0 cubic feet is 3.70 yards, about 5.0 tons. At this size, a bulk delivery usually beats a cart full of bags once you count trips. Compare the bag price × 200 against a bulk quote for 5.5 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 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.

When to choose river rock

Best suited to:

Dry creek beds and drainage swales
Decorative borders and planting beds
Around downspouts to stop splash erosion

Think twice for:

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 14x28 area at 2 inches takes about 3.3 tons.
Weight used here: about 1.35 tons per cubic yard.

Mistakes that throw off the order

Skipping drainage. Water sitting under any surface softens the base and leads to ruts and potholes.
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.
Measuring only the main rectangle. Aprons, turnouts and curved edges add real square footage.

Questions people ask

How many bags of river rock for a 20x20 patio?

About 200 bags of 0.5 cubic feet at 3 inches deep.

How many 50 lb bags of river rock for 20x20?

About 200 bags at 3 inches.

How many 0.5 cubic foot bags are in a cubic yard?

54 bags.

How many cubic feet is a 20x20 patio at 3 inches?

About 100.0 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.

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