Bags of River Rock for a 20x24 Patio

How many bags of river rock for a 20x24 patio: at 3 inches deep you need about 120.0 cubic feet, which is 240 bags of the common 0.5 cubic foot size. If your store sells river rock in 50-pound bags instead, figure about 240 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	40.0	80	80
2 in	80.0	160	160
3 in	120.0	240	240
4 in	160.0	320	320

How to figure it

Area: 20 × 24 = 480 sq ft.
Volume: 480 × (3 ÷ 12) = 120.0 cu ft.
Bags: 120.0 ÷ 0.5 = 240 bags (round up).

Bags or bulk?

A cubic yard is 27 cubic feet, so 120.0 cubic feet is 4.44 yards, about 6.0 tons. Past about a yard, bulk is usually less work and often less money. Compare the bag price × 240 against a bulk quote for 6.6 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.

Good and poor uses for river rock

Best suited to:

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

Poor fit 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 8x16 area at 3 inches takes about 1.6 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.
Ignoring the base. A thin surface layer over soft soil fails early no matter how much material is on top.
Using inches as if they were feet. Depth has to be divided by 12 before you multiply; skipping that step inflates the order twelvefold.
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 20x24 patio?

About 240 bags of 0.5 cubic feet at 3 inches deep.

How many 50 lb bags of river rock for 20x24?

About 240 bags at 3 inches.

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

54 bags.

How many cubic feet is a 20x24 patio at 3 inches?

About 120.0 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.

As an Amazon Associate, AsphaltTons.com earns from qualifying purchases. Product links below are sponsored.