River Rock Calculator
River rock in cubic yards, tons and bags
Why a range and not one number: river rock is quoted at about 3,000 lb per cubic yard, but the real figure runs from 2,800 to 3,500 lb. Rounded stone, 1.4 to 1.75 tons per cubic yard depending on stone size. Larger stone packs with more void space and weighs less per yard. Order against the cubic yards — suppliers convert to tons using their own material’s density, and that is the number that should win.
The calculation
cubic yards = (length x width x depth in inches / 12) / 27
The two conversions in that line are where the mistakes happen. Depth is quoted in inches while the area is in feet, so it must be divided by 12 first; and a cubic yard is 27 cubic feet, not 3, because it is 3 ft in each of three directions.
How deep should it go?
| Use | Typical depth |
|---|---|
| Decorative bed cover | 2-3 in for full coverage |
| Dry creek bed | 4-6 in, deeper in the channel |
| Drainage around a downspout | 3-4 in over landscape fabric |
| Larger 2-3 in stone | allow more depth, since fewer stones cover the same area |
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Frequently Asked Questions
How do I work out how much river rock I need?
Multiply the area by the depth, then convert to cubic yards. A bed 20 ft by 10 ft at 3 in deep is 200 sq ft x 0.25 ft = 50 cubic feet, and 50 / 27 = 1.85 cubic yards. Depth is the input people get wrong, because it is given in inches while everything else is in feet.
How many tons is a cubic yard of river rock?
About 1.50 US tons, using a typical density of 3,000 lb per cubic yard. The honest range is 1.40 to 1.75 tons. Rounded stone, 1.4 to 1.75 tons per cubic yard depending on stone size. Larger stone packs with more void space and weighs less per yard.
Should I order by cubic yards or by tons?
By cubic yards wherever you can. Volume is fixed by your measurements, while tonnage depends on the density of the specific material on the day — including how wet it is. If a supplier quotes tons, let them do the conversion from your yardage using their own density.
Should I add extra for settling?
Usually yes. Loose material compacts once it is spread and walked on, and every job loses a little to spillage and uneven subgrade. Ordering 5 to 10 percent over the calculated volume is normal; running short mid-job costs a second delivery charge.