River Rock Calculator
To figure how much river rock you need, multiply length × width × depth in feet and divide by 27 for cubic yards, then multiply by about 1.35–1.5 for tons. For example, a 10 × 10 ft bed 3 inches deep needs 0.93 cubic yards, or about 1.25–1.39 tons.
How to calculate river rock
- Measure the area. Measure the length and width in feet, or use the area in square feet if you know it.
- Choose the depth. Spread river rock at least as deep as the largest stones, so they cover the ground in one layer. Divide the depth in inches by 12.
- Find the cubic yards. Multiply length × width × depth to get cubic feet, then divide by 27.
- Convert to tons. Multiply the cubic yards by 1.35–1.50 for small to medium river rock, or by 1.31–1.40 for large river rock and cobble.
- Round up. Round up to what your supplier sells. For bags, divide the cubic feet by the bag size printed on the bag.
Worked example: a 20 × 4 ft border 2 inches deep: 20 × 4 × (2 ÷ 12) = 13.33 cubic feet, and 13.33 ÷ 27 = 0.49 cubic yards. At 1.35–1.50 tons per cubic yard, that's 0.67–0.74 tons of river rock.
How much does river rock weigh?
These are loose weights, as delivered, and they match the rock and stone calculator. Wet rock weighs more.
| Stone size | Tons per yd³ | Lb per yd³ | Yd³ per ton |
|---|---|---|---|
| Small to medium (¾–3 in) | 1.35–1.50 | 2,700–3,000 | 0.67–0.74 |
| Large (3–8 in) and cobble | 1.31–1.40 | 2,610–2,800 | 0.71–0.77 |
How much does a ton of river rock cover?
One cubic yard covers 324 sq ft divided by the depth in inches. Large stones need at least 3 inches to cover the ground, so their column starts there.
| Depth | Small to medium | Large (3–8 in) |
|---|---|---|
| 1 in | 216–240 sq ft | — |
| 2 in | 108–120 sq ft | — |
| 3 in | 72–80 sq ft | 77–83 sq ft |
| 4 in | 54–60 sq ft | 58–62 sq ft |
| 6 in | 36–40 sq ft | 39–41 sq ft |
River rock sizes
River rock is sold by stone size. Spread it at least as deep as the largest stones so it covers the ground in one layer:
- ¾–1 inch: the smallest river rock; at least 1 inch deep. Uses the small to medium weight.
- 2 inch: at least 2 inches deep. Small to medium weight.
- 1–3 inch: the most common mix; about 3 inches deep so the larger stones sit in one layer. Small to medium weight.
- 3–5 inch: at least 5 inches deep. Uses the large weight.
- 4–8 inch cobble: laid one stone deep, so enter a depth close to the stone size. Large weight.
For lava rock, base rock or other landscape rock, use the rock and stone calculator.
River rock quick reference: 1 to 10 tons
| Tons | Cubic yards | Covers at 2 in | Covers at 3 in |
|---|---|---|---|
| 1 | 0.67–0.74 | 108–120 sq ft | 72–80 sq ft |
| 2 | 1.33–1.48 | 216–240 sq ft | 144–160 sq ft |
| 3 | 2.00–2.22 | 324–360 sq ft | 216–240 sq ft |
| 4 | 2.67–2.96 | 432–480 sq ft | 288–320 sq ft |
| 5 | 3.33–3.70 | 540–600 sq ft | 360–400 sq ft |
| 10 | 6.67–7.41 | 1,080–1,200 sq ft | 720–800 sq ft |
Frequently asked questions
How much river rock do I need?
Multiply length × width × depth in feet, divide by 27, then multiply by about 1.35–1.5 for tons. A 10 × 10 ft bed 3 inches deep needs 0.93 cubic yards, about 1.25–1.39 tons.
How do you calculate river rock?
Measure length and width in feet, divide the depth in inches by 12, multiply for cubic feet and divide by 27. A 20 × 4 ft border 2 inches deep is 13.33 cubic feet, or 0.49 cubic yards (about 0.67–0.74 tons).
How much does a ton of river rock cover?
About 108–120 sq ft at 2 inches deep, 72–80 sq ft at 3 inches and 54–60 sq ft at 4 inches, for small to medium river rock at 1.35–1.50 tons per cubic yard. Large river rock laid 4 inches deep covers about 58–62 sq ft per ton.
How much river rock is in a yard?
A yard is one cubic yard: 27 cubic feet, a cube 3 feet on each side. It weighs about 1.35–1.50 tons (2,700–3,000 lb) of small to medium river rock and covers 108 sq ft at 3 inches deep.
How much 1–3 inch river rock do I need?
Spread 1–3 inch rock about 3 inches deep so the larger stones sit in one layer. At that depth a ton covers about 72–80 sq ft, and one cubic yard covers 108 sq ft and weighs 1.35–1.50 tons.
How much 2 inch river rock do I need?
Spread 2-inch river rock at least 2 inches deep. At 2 inches, a ton covers about 108–120 sq ft and a cubic yard covers 162 sq ft.
Related calculators
Sources and methodology
Volumes use (length × width × depth) ÷ 27 with all measurements in feet. Weights are loose, as delivered, and are the same as on the rock and stone calculator: small to medium river rock runs from the Federal Highway Administration's figure for dry, uniformly graded gravel to Penn State's figure for AASHTO #57 stone; large river rock and cobble from FHWA's riprap rock to Penn State's R-3 to R-6 riprap. That's why results show a range. Wet rock weighs more. Bags are cubic feet ÷ bag size, rounded up; a cubic yard is 54 bags of 0.5 cu ft. Order amounts are rounded up to the next half cubic yard or half ton. Tons are US short tons (2,000 lb).