The conversion
From a measured layer to a tonnage estimate
Square footage and finished depth give you volume. The seller’s loose bulk weight converts that volume to short tons. This weight includes the air spaces between stones; it is different from the density of an individual rock.
cubic yards = area (sq ft) × depth (in) ÷ 324short tons = cubic yards × loose short tons per yd³For the starting example: 300 × 3 ÷ 324 = 2.78 yd³. At 1.35 tons/yd³, the layer weighs about 3.75 tons. Multiplying by 1.10 for the chosen 10% extra gives 3.06 yd³, or 4.13 tons to order.
The 324 divisor combines 12 inches per foot and 27 cubic feet per cubic yard. The 1.35 multiplier is an editable planning assumption, not a guaranteed product weight.
The depth decision
One ton covers less ground as the layer gets deeper
These yields assume 1.35 US short tons per cubic yard, a flat layer, and no extra allowance. They are conversion examples, not promises about the appearance of a particular stone size. A mixed 1–3 in river rock often starts around a 3 in planning depth; inspect the actual grade before committing to a full order.
| Installed depth | One cubic yard covers | One short ton covers |
|---|---|---|
| 2 in | 162 sq ft | 120 sq ft |
| 3 in | 108 sq ft | 80 sq ft |
| 4 in | 81 sq ft | 60 sq ft |
| 6 in | 54 sq ft | 40 sq ft |
If the project is a dry creek, measure the stone-lined bottom and banks by section. This tool estimates quantity; it does not size rock for flowing water. See the dry creek bed guide for that separate design question.
Before paying for a load
Check the weight attached to the seller’s stone
Supplier listings illustrate why the weight field is editable: Rocky Top Resources uses an approximate 1.30-ton-per-cubic-yard rock conversion on its 1–2 in gray river rock listing, while Kent Countryside lists about 1.40 tons per cubic yard for 3/8 in river rock. This calculator starts at 1.35; use the figure for the stone you actually select.
Each comparison uses the same 300 sq ft bed, 3 in installed depth, and 10% extra. Only the assumed loose bulk weight changes.
- Confirm the exact grade. “River rock” can include widely different size mixes and amounts of fines; ask to see a sample.
- Confirm the unit. A quote by the ton and a quote by the cubic yard need the seller’s tons-per-yard factor to compare.
- Confirm delivery limits. Ask about the minimum order, available truck payload, delivery fee, and where the load may be tipped. Do not treat a generic truck-load figure as universal.
- Keep moisture separate. ASTM C29/C29M describes bulk density testing for aggregate up to 5 in nominal maximum size; it does not assign river rock a universal 1.35 value. Stockpile moisture and placement can make a delivery differ from a dry test value.
Need volume or bag quantities instead? Use the river rock cubic yard calculator or river rock bag calculator. To work backward from a known tonnage to square feet, use the river rock coverage calculator.
River rock tonnage questions
How many tons of river rock do I need for 300 square feet?
At 3 inches deep, 300 square feet needs 2.78 cubic yards before extra. At the 1.35 short tons per cubic yard planning weight, that is 3.75 short tons. With 10% extra, the order estimate is 3.06 cubic yards or 4.13 short tons. Replace the planning weight with your supplier’s value when possible.
How do I turn cubic yards of river rock into tons?
Multiply cubic yards by the loose bulk weight in US short tons per cubic yard for the product you are buying. For example, 3 cubic yards at 1.35 short tons per cubic yard is an estimated 4.05 short tons. A short ton is 2,000 pounds.
How much area does one ton of river rock cover?
At the calculator’s 1.35 short tons per cubic yard planning value, one short ton covers about 120 square feet at 2 inches deep, 80 square feet at 3 inches, or 60 square feet at 4 inches. This is level-layer coverage before any ordering allowance.
Is a 6-inch river rock a 6-inch-deep layer?
A stone-size label describes the rocks, not the layer thickness. Large mixed cobbles placed in one visible layer do not form a uniform blanket, so a depth-based tonnage is only a rough estimate. Ask the stone yard about coverage for that exact grade or lay out a measured sample area.
Does the extra allowance cover wet rock?
The extra percentage adds order volume for low spots, uneven spreading, and handling loss. It does not predict how much a wet load will weigh. Ask the seller how its tons-per-yard conversion and scale weight are determined.