River Rock Calculator
A river rock calculator converts bed area and depth to tons at 1.4 tons per cubic yard. A 20 × 10 ft bed at 2 in deep needs 1.73 tons, or 1.90 tons with waste.
What your order looks like
A pickup or a small delivery will do it.
1.23 yd³ · 1.7 tons
17 wheelbarrow trips (2 cu ft each)
3 pickup loads (0.75 ton each)
1 small dump truck load (6 tons each)
Rules of thumb: A wheelbarrow trip is 2 cubic feet of heavy material, about 200 lb, a load most people can push. A pickup load is 0.75 ton, the payload of a full-size half-ton pickup (1,500 lb). A small single-axle dump truck carries about 6 tons.
A river rock calculator converts the area of a bed and the depth of the layer into tons. It finds cubic yards first, then multiplies by 1.4 tons per cubic yard. A 20 ft by 10 ft bed at 2 inches deep is 1.23 cubic yards, or 1.73 tons.
The formula in plain words
Multiply length by width to get the area. Multiply that by the depth in feet, which is the inches divided by 12. Divide by 27 to turn cubic feet into cubic yards.
Rock is sold by weight, so multiply the cubic yards by 1.4 to get tons. If you tick the waste box, the calculator adds 10% to the tons. Multiply the tons by your price per ton for the cost.
Worked examples
Example 1, the default: 20 ft by 10 ft, 2 inches deep, $80 per ton.
- Area: 20 × 10 = 200 sq ft
- Volume: 200 × (2 ÷ 12) = 33.33 cu ft, and 33.33 ÷ 27 = 1.235 cu yd
- Tons: 1.235 × 1.4 = 1.73 tons
- Cost: 1.728 × $80 = $138.27
- With 10% waste: 1.728 × 1.10 = 1.90 tons, $152.10
Example 2, a dry creek path: 30 ft by 4 ft, 3 inches deep.
- Area: 30 × 4 = 120 sq ft
- Volume: 120 × 0.25 = 30 cu ft, or 1.111 cu yd
- Tons: 1.111 × 1.4 = 1.56 tons
- With 10% waste: 1.71 tons, or $136.89 at $80
Coverage per ton
| Depth | Area covered by 1 ton |
|---|---|
| 1 in | about 231 sq ft |
| 2 in | about 116 sq ft |
| 3 in | about 77 sq ft |
| 4 in | about 58 sq ft |
These follow from 1 ton being 0.714 cu yd, or 19.3 cu ft. Spread 19.3 cu ft at a depth of 2 inches (0.167 ft) and it covers 19.3 ÷ 0.167 = 116 sq ft.
How to measure
Measure the length and width of the bed itself, leaving out the edging. For curved beds, take the longest length and the average of three widths. For irregular shapes, split the bed into rectangles, run each through the calculator, and add the tons.
Check the depth at the bed’s low spots as well as the average. A bed that dips in the middle needs more rock there to hide the fabric.
Common mistakes
- Using too thin a layer. At 1 inch the ground or fabric shows through the gaps between stones.
- Forgetting the base. Rock on bare soil sinks over a season or two. A fabric layer or a gravel base helps.
- Choosing river rock for a driveway. Round stone shifts under tires.
- Ignoring a slope. Rock rolls downhill, so a slope needs edging or a deeper layer at the bottom.
- Ordering by the cubic foot figure from a bag size without checking the weight per bag.
Ordering bulk, bags, or wheelbarrow loads
For the default bed, 1.728 tons is 3,456 lb. If the stone came in 40 lb bags, that is 3,456 ÷ 40 = 86.4, or 87 bags. Bulk delivery by the ton is usually the practical way to buy this much.
To move it, count wheelbarrows. The bed holds 33.3 cu ft, and a wheelbarrow carries about 6 cu ft, so it is 5.6 loads, rounded up to 6. With the 10% waste added, 36.7 cu ft is 6.1 loads, or 7. Ask the supplier to drop the pile close to the bed to save steps.
Edging and slopes
Stone spreads past a bed that has no edge. Steel, stone, or plastic edging holds the layer in and keeps lawn grass out. On a slope, rock slides downhill over time, so build the bed with a lip at the bottom and consider a thicker layer there. Add the extra depth to the measurement and run the section by itself.
Related calculators
For a cheaper or smaller stone, see the pea gravel calculator or the general gravel calculator. The landscape rock calculator covers other decorative stone, and the landscape fabric calculator counts the rolls to put underneath.
Frequently asked questions
Why is river rock more expensive than crushed gravel?
River rock is sorted, washed, and sold as a decorative product, and its rounded shape and color are the selling point. Crushed gravel is a bulk construction material. The calculator lets you enter any price per ton: at $80, 1.73 tons costs $138.27 and at $120 it costs $207.41.
How deep should a river rock layer be?
Two to three inches is common for a decorative bed, deep enough to hide the ground or fabric. Larger rock needs more depth to cover. At 2 inches one ton covers about 116 sq ft, and at 3 inches about 77 sq ft.
Do I need landscape fabric under river rock?
Fabric keeps rock from sinking into soft soil and slows weeds from coming up through the layer. Many installers put it down, then add the rock. It does not stop weeds that land on top of the rock and sprout in dust, so occasional weeding is still needed.
Is river rock's density different from other gravel?
In this calculator, river rock uses 1.4 tons per cubic yard, the same as standard and pea gravel. Real loads vary with rock type, size, and moisture. If your supplier quotes a different weight per yard, use their number.
What size river rock should I use for a landscape bed?
Beds commonly use stones from about 1 to 3 inches across. Smaller stones are easier to walk on and rake, and larger stones look more natural in a dry creek bed or near a downspout. Look at the stone in person, since sizes and colors vary by supplier.
Estimates only. Verify quantities with your supplier before purchasing.