RIVER ROCK
River rock calculator
Cubic yards of river rock = square feet × depth in inches ÷ 324, and cubic feet = square feet × depth in inches ÷ 12. River rock is a shape and a finish, not a different unit of measure — the volume arithmetic is identical to every other bulk material.
Worked example
A 150 sq ft border at 2 inches: 150 × 2 ÷ 12 = 25 cubic feet, and 150 × 2 ÷ 324 = 0.93 cubic yards.
In bags, divide by the cubic feet the bag states and round up. A 25 cubic foot job in half-cubic-foot bags is 50 bags — which is the moment most people switch to ordering by the yard. Convert the bag price to price per cubic foot before deciding; the yard price check shows the same conversion for mulch.
How river rock differs from other landscape stone
This is where river rock separates from crushed rock and from the decorative types covered by the landscape rock calculator, and it is about behaviour rather than volume:
| River rock (smooth, rounded) | Crushed rock (angular) | |
|---|---|---|
| How it settles | Particles roll and do not interlock | Angular faces lock together |
| Underfoot | Moves; uncomfortable as a walking surface | Firms up when compacted |
| Load bearing | Poor — unsuitable as a base course | Used as base and sub-base |
| Containment | Essential; it spreads without edging | Less prone, still needs edging |
| Typical use | Decorative beds, dry creek beds, borders | Driveways, paths, drainage |
None of that changes the cubic yards. It changes where you can put it and what has to be under it.
Depth is the input that matters
River rock is usually decorative, so the depth is a visual and practical choice: deep enough to hide the membrane, deep enough not to scrape through when walked on, and deep enough to look like a bed of stone rather than a scattering. Because rounded stone exposes more of the membrane between particles at shallow depth than angular stone does, the "just enough to cover" depth for river rock is generally not the same as for crushed rock of the same size.
Decide the depth from the look and the use, then convert. This page will not print a depth table for the same reason the rest of this site does not: it would be guessing at your site.
Weight, and why the quote may come in tons
Stone is often priced by weight, and converting your cubic yards to tons needs the density of that particular stone. River rock is a description of shape and origin, not a single material — the density varies with what the stone is and how it is graded, and moisture moves the figure too. Ask the supplier for their pounds per cubic yard for the product you are buying, or ask them to quote in cubic yards. This page will not supply a density it cannot stand behind, for the same reason the gravel calculator will not supply a tonnage figure.
Ordering checklist
- Net area with shrub and trunk footprints taken off.
- Depth chosen for the look and the use.
- Membrane and edging in place first — neither changes the volume, both change the result.
- The unit you are buying in: cubic yard, bag, or ton, and the density if it is tons.
- A waste allowance, decided once and applied to the total.
Related calculators
Landscape rock calculator for decorative and crushed types with the supplier-published coverage figures · How much landscape rock do I need for the step-by-step measuring version · Pea gravel calculator for small rounded aggregate sold in half-cubic-foot bags.
The arithmetic is from the definitions 1 cubic yard = 27 cubic feet and 1 foot = 12 inches. No density figure is published here: density is product specific and belongs to the supplier. The coverage-per-depth relationship is the same one NC State Extension’s Organic Lawn Care, appendices (read 2026-09-21) states for compost (one cubic yard covering 108 sq ft at 3 inches, 216 at 2 inches, 324 at 1 inch, read 2026-09-21).