How to calculate how much river rock you need
- Measure the length and width of the bed in feet and multiply them for square feet. For a round bed, use 3.14 × radius².
- Multiply by the depth in inches ÷ 12 to get cubic feet.
- Divide by 27 for cubic yards.
- Multiply by 1.4 for 1 to 3 inch rock, or by about 1.25 for 3 to 5 inch rock, to get tons.
Worked example. A dry creek bed 20 ft long and 4 ft wide, 3 inches deep: 80 ft² × 0.25 ft = 20 ft³. 20 ÷ 27 = 0.74 yd³, or about 1.04 tons of 1 to 3 inch river rock.
How deep to lay river rock
| Use | Depth | One ton covers (1 to 1.5 in rock) |
|---|---|---|
| Planting beds, ground cover | 2 in | 100–120 ft² |
| Paths and foot traffic | 3 in | 65–80 ft² |
| Dry creek beds, drainage | 4 in | About 50–60 ft² |
Big 3 to 5 inch stones are usually laid one stone deep, so set the depth to about the size of the rock. For small, smooth stone underfoot, the pea gravel calculator fits better.
How much does river rock weigh?
Mulch Mound puts 1 to 3 inch river rock at about 1.4 to 1.5 tons per cubic yard and 3 to 5 inch rock at about 1.2 to 1.3 tons, because large stones leave bigger gaps. Wet rock weighs more. Our guide to how much a yard of gravel weighs compares river rock with crushed stone, pea gravel and other materials.
Laying river rock
- Dig out the bed so the rock sits level with or just below the lawn edge.
- Lay landscape fabric and pin the seams.
- Set metal or stone edging so the rock stays put.
- For a dry creek bed, put the biggest stones along the sides and smaller rock in the channel.
Planting the bed too? Work out the soil with the topsoil calculator. For shoreline and slope protection with much bigger stone, use the rip rap calculator.
Questions about river rock
How many square feet does a ton of river rock cover?
About 100 to 120 ft² at 2 inches deep and 65 to 80 ft² at 3 inches for 1 to 1.5 inch rock. Larger stone covers less per ton.
How deep should river rock be?
About 2 inches for planting beds, 3 inches for paths and 4 inches for dry creek beds and drainage channels.
Should I put fabric under river rock?
Landscape fabric under the rock slows weeds and keeps stones from sinking into the soil. In planting beds, cut openings for the plants.
Is river rock the same as pea gravel?
Both are smooth and rounded, but pea gravel is under about 3/8 inch while river rock is usually 1 inch and up. Pea gravel suits paths you walk on; river rock is mostly decorative and for drainage.
Sources
- River rock weight: 1 to 3 inch rock about 1.4 to 1.5 tons per cubic yard, 3 to 5 inch rock about 1.2 to 1.3: Mulch Mound, How Many Tons of River Rock Do You Need?
- Depths: 2 inches for beds, 3 inches for paths, 4 inches for dry creek beds: Mulch Mound, How Many Tons of River Rock Do You Need?
Last reviewed November 9, 2026. Found a wrong figure? Tell us.