How Much River Rock for a 12x18 Patio?
How much river rock for a 12x18 patio: at 3 inches deep you need about 2.00 cubic yards, which is roughly 2.7 tons at 1.35 tons per yard. The patio covers 216 square feet, so every inch of depth adds about 0.67 yards.
Volume and tonnage calculator →The math for a 12x18 patio
- Area: 12 × 18 = 216 sq ft.
- Depth in feet: 3 ÷ 12 = 0.250 ft.
- Cubic feet: 216 × 0.250 = 54.0 cu ft.
- Cubic yards: ÷ 27 = 2.00 yd³.
- Tons: × 1.35 = 2.7 tons.
The volume and tonnage calculator does this for any size.
River rock needed by depth
| Depth | Cubic yards | Tons (approx.) | Tons +10% |
|---|---|---|---|
| 2 in | 1.33 | 1.8 | 2.0 |
| 3 in | 2.00 | 2.7 | 3.0 |
| 4 in | 2.67 | 3.6 | 4.0 |
About river rock
River rock is mostly decorative and for drainage beds. It is not meant to be driven on and tends to roll if used as a walking surface. If the yard sells by the cubic yard instead of the ton, use the cubic-yard column directly.
Preparing the patio
Remove sod, level the area with a slight slope away from the house, and lay landscape fabric if weeds are a concern. Edging keeps loose material inside the patio footprint. This patio sees foot traffic and furniture, so match the depth to that load rather than to the minimum.
Ordering tips
- Round up. Compaction and uneven ground eat material. Adding about 10 percent is common.
- Delivery size. 3.0 tons fits in a single typical dump truck load; small loads may carry a delivery fee. See how many tons of gravel in a dump truck.
- Bulk vs bags. At this size bulk delivery is usually the practical choice.
- Where it drops. Have the truck dump as close to the patio as firm ground allows.
Where river rock fits
Works well for:
- 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 15x30 area at 3 inches takes about 5.6 tons.
- Weight used here: about 1.35 tons per cubic yard.
Where estimates go wrong
- Measuring only the main rectangle. Aprons, turnouts and curved edges add real square footage.
- Assuming every supplier uses the same weight. Two yards selling the same product name can quote different tons per yard.
- Using inches as if they were feet. Depth has to be divided by 12 before you multiply; skipping that step inflates the order twelvefold.
- Forgetting that compaction shrinks loose material. A loose 4-inch spread of a dense-graded stone may finish closer to 3 inches after rolling.
Questions people ask
How many tons of river rock for a 12x18 patio?
About 2.7 tons at 3 inches deep, or 3.0 tons with 10 percent extra.
How many cubic yards is a 12x18 patio at 3 inches?
About 2.00 cubic yards.
How much does a cubic yard of river rock weigh?
Usually around 1.25 to 1.45 tons, depending on stone size, fines and moisture.
How deep should river rock be for a patio?
The table above shows 2 to 4 inches. Shallower depths suit top dressing; deeper depths suit new installs and heavier use.
How many square feet is 12x18?
216 square feet.
Related guides
- How Much Does a Ton of River Rock Cover?
- Tons to Cubic Yards for Gravel: Conversion Chart
- How Many Tons of Gravel in a Dump Truck? Loads and Coverage
- How Much Does a Ton of Gravel Cover? Depth Chart
- How Much River Rock for a 12x14 Patio?
- How Much River Rock for a 12x16 Patio?
As an Amazon Associate, AsphaltTons.com earns from qualifying purchases. Product links below are sponsored.