Box / room
Also: rectangular prism, bed, trench, room
V = L × W × H
L = length, W = width, H = height or depth.
Example: A bed along a fence, 20 × 4 ft, 3 in deep: 20 × 4 × 0.25 = 20 cu ft = 0.74 cu yd, about 0.95 tons.
Quick answer: tons of river rock = length × width (ft) × depth (in) ÷ 12 × 95 ÷ 2,000. A ton covers about 84 sq ft at 3 in deep.
How to calculate how much river rock you need
- Measure each bed in feet and choose a depth in inches (see the depth guide below).
- Cubic feet = length × width × (depth ÷ 12).
- Cubic yards = cubic feet ÷ 27.
- Tons = cubic feet × 95 ÷ 2,000.
Tons = L (ft) × W (ft) × depth (in) ÷ 12 × 95 ÷ 2,000
A 20 × 4 ft bed, 3 in deep:
20 × 4 × 3 ÷ 12 = 20 cu ft = 0.74 cu yd. 20 × 95 ÷ 2,000 = 0.95 tons, or 40 bags of 0.5 cu ft. With 5% extra: about 1 ton.
How far a ton of river rock goes
| Depth | 1 ton covers | 1 cu yd covers |
|---|---|---|
| 2 in | 126 sq ft | 162 sq ft |
| 3 in | 84 sq ft | 108 sq ft |
| 4 in | 63 sq ft | 81 sq ft |
| 6 in | 42 sq ft | 54 sq ft |
How deep should river rock be?
A common rule of thumb is a layer about twice as deep as the stones are wide, so the fabric underneath doesn’t show:
| Stone size | Typical depth | Good for |
|---|---|---|
| ¾–1½ in | 2 in | Beds, paths, around plants |
| 1–3 in | 3–4 in | Beds, borders, downspout splash areas |
| 3–5 in | 5–6 in | Dry creek beds, drainage swales |
How much river rock weighs
The calculator uses 95 lb per cu ft, about 1.28 tons per cubic yard. That is an estimate: rounded stone made of rock with a specific gravity of about 2.65, with roughly 40% air space between the stones, weighs 2.65 × 62.4 × 0.6 ≈ 99 lb per cu ft. Rock type, stone size and moisture all change it, so treat tons as an estimate. If your supplier quotes a weight, enter it as a custom density.
River rock for different shapes
Area × depth
Also: square feet to cubic feet
V = A × d
A = area, d = depth or thickness.
Example: Side-yard beds adding up to 300 sq ft, 2 in deep: 300 × 0.167 = 50 cu ft = 1.85 cu yd, about 2.4 tons.
Cylinder
Also: round hole, post hole, tank, planter
V = π × r² × h
r = radius (half the diameter), h = height.
Example: A round bed 6 ft across, 3 in deep: π × 3² × 0.25 = 7.1 cu ft, about 0.34 tons (680 lb).
Ring / tree ring
Also: around a tree, donut bed, circle with a hole
V = π × (R² − r²) × d
R = outer radius, r = inner radius (the part left bare), d = depth.
Example: A ring 6 ft across around a tree, with 2 ft around the trunk left bare, 3 in deep: π × (3² − 1²) × 0.25 = 6.3 cu ft, about 0.30 tons.
Trench / trapezoid
Also: ditch, berm, swale, trapezoidal prism
V = (a + b) ÷ 2 × h × L
a = top width, b = bottom width, h = depth, L = length.
Example: A dry creek bed 30 ft long, 3 ft wide at the top and 1.5 ft at the bottom, 12 in deep: (3 + 1.5) ÷ 2 × 1 × 30 = 67.5 cu ft = 2.5 cu yd, about 3.2 tons.
Worked examples
Dry creek bed
A channel 30 ft long, 3 ft across the top, 1.5 ft across the bottom and 12 in deep: 67.5 cu ft = 2.5 cu yd, about 3.2 tons. Line it with fabric, and set a few larger boulders along the edges.
Around the house
A 2 ft strip along 120 ft of foundation, 3 in deep: 120 × 2 × 0.25 = 60 cu ft = 2.2 cu yd, about 2.9 tons.
- Need crushed stone for a path or base? Use the stone calculator. For smaller round stone, try the pea gravel calculator.
Frequently asked questions
How much river rock do I need?
Multiply length × width in feet by the depth in inches ÷ 12 to get cubic feet. Multiply by about 95 lb per cu ft and divide by 2,000 for tons. A 20 × 4 ft bed 3 in deep is 20 cu ft, 0.74 cu yd or about 0.95 tons.
How much does a ton of river rock cover?
About 21 cu ft, which covers roughly 126 sq ft at 2 in deep, 84 sq ft at 3 in and 63 sq ft at 4 in. Bigger stones need a deeper layer, so they cover less.
How much does a yard of river rock weigh?
The calculator estimates about 2,565 lb (1.28 tons) per cubic yard, from 95 lb per cu ft. Real loads vary with the rock and its moisture; enter your supplier’s figure as a custom density if you buy by the ton.
How deep should river rock be?
A common rule of thumb is a layer about twice as deep as the stones are wide: about 2 in for ¾–1½ in stone and 3–4 in for 1–3 in stone. That is enough to hide the fabric underneath.
Should I put landscape fabric under river rock?
Usually, yes. A woven or non-woven landscape fabric keeps the stones from sinking into the soil and slows weeds. Overlap the seams and pin them down.
Is river rock cheaper by the ton or in bags?
Bulk river rock by the ton is usually much cheaper than 0.5 cu ft bags for more than a few hundred pounds. A ton is about 42 bags of 0.5 cu ft. Enter both prices to compare.
Is river rock good for a driveway?
Not as the main surface. Smooth, round stones roll under tires and don’t lock together. For driveways use crushed stone, and keep river rock for beds, borders and dry creek beds.
Is this river rock calculator free to use online?
Yes. The CalcWall River Rock Calculator is completely free and works online in any browser, on a phone, tablet or computer. There is nothing to download and no account to create, and the math runs right in your browser, so results appear as you type.