Yards are exact. Tons are your supplier's.
Every river rock calculator online will happily convert your volume into
tons. None of them can tell you where the density came from, because
there is no published figure to cite: river rock is graded by size and
sold decoratively, and its weight per yard moves with the grade, the
roundness and how wet the pile is. So this page gives you an exact volume
and a blank weight field, and asks the one party who actually knows.
yd³ = area (ft²) × depth (in) ÷ 12 ÷ 27
200 ft² at 3 in
50 ft³
1.85 yd³
1.42 m³
Tons appear when you enter a density.
Depth follows the stone size
The rule that keeps a bed looking right: the layer should be at least
twice the largest stone in it. A three-quarter inch grade sits happily at
two inches. A two-inch cobble at two inches deep is a single layer of
stones with fabric visible between them, and it will look like exactly
that. Dry creek beds and drainage runs want three to four inches, partly
for looks and partly because the depth is what stops the stone shifting.
Cubic yards by area and depth
From this calculator with no waste allowance. Volumes are exact. Tons are whatever your supplier publishes for their own product — there is no national figure for decorative river rock.
Grades do different jobs
- ¾ to 1½ in — beds, borders and paths, where an even surface matters.
- 2 to 5 in cobble — dry creek beds, splash zones and slopes, where the weight of the stone is what keeps it in place.
- Mixed — a creek bed reads as natural when the sizes vary, and it costs nothing extra to buy two grades and place them.
Fabric underneath, and an edge around
Fabric because rock works down into soft ground, and a layer that thins
out is worse than one that was thin to start with. An edge because
rounded stone rolls: on a slope, on a lawn boundary, anywhere it can go
it will. Both are cheaper to do first than to retro-fit, which means
moving the stone twice.
Delivery is most of the decision
Decorative stone is heavy, low in value per ton and expensive to move, so
on a small job the delivery charge and the yard's minimum load usually
matter more than the per-yard rate. The tool has fields for both and
reports what the load actually costs per yard once you have paid for a
minimum you cannot spread.
The rest of the job
Under it, the
landscape fabric calculator
counts rolls with the seams paid for. For a finer decorative stone the
pea gravel calculator
works the same way, and for a buried drain — which wants angular stone
rather than rounded — the
french drain calculator
sizes the trench, the pipe and the wrap. If you are excavating for the
bed first, the excavation calculator
gives you what comes out and how much bigger it gets, and the
flagstone calculator
covers the stepping stones you set into it.
Common questions
How much river rock do I need?
Area times depth. Two hundred square feet at three inches is 50 cubic feet, which is 1.85 cubic yards. The volume is exact and it is the number to order against — river rock is sold by the yard as often as by the ton, and the yard is the figure that does not depend on anybody's density estimate.
How many tons is a yard of river rock?
Nobody publishes a figure worth citing, so this page does not print one. River rock is a graded decorative product, not a specification aggregate: its weight per cubic yard moves with the size grade, how rounded it is and how wet it is, and every number you will find quoted online traces back to somebody's estimate rather than a test. Your supplier knows what theirs weighs. Enter their figure and the tool gives you tons.
How deep should river rock be?
Two inches over fabric in a decorative bed, three to four for a dry creek bed or a drainage run, and more for the larger grades — a stone two inches across needs a layer deeper than two inches to sit in rather than on. As a rule, the depth should be at least twice the largest stone, or the layer looks sparse and the fabric shows through between pieces.
What size river rock should I use?
Small grades — around three quarters to one and a half inches — for beds and paths, where you want an even surface. Larger cobbles, two to five inches, for dry creek beds, splash zones and slopes, where the weight is what stops the stone moving. Mixing grades looks more natural in a creek bed than a single size does, and costs nothing extra if you buy them separately and place them.
Does river rock need landscape fabric under it?
Yes, and it is one of the few places fabric is a genuinely good idea. Stone does not break down into a seed bed on top of the barrier the way bark mulch does, so it stays a barrier. Its more important job is separation: without it, rock works down into soft ground and a three inch layer becomes patchy in a couple of seasons. Use the fabric calculator, which counts the seam overlap that area-based estimates miss.
Can river rock be used for drainage?
For a surface swale or a dry creek that carries runoff, yes — rounded stone is exactly what you want on the surface, because it does not shift when water moves over it. For a buried french drain, no: that wants washed angular stone around a perforated pipe, sized so the voids stay open. The french drain calculator handles that build, including wrapping the trench in fabric rather than just lining the bottom.
How much does a project cost?
The volume above is ours and it is exact; the rate is yours and it is intensely local, because decorative stone is heavy, low value per ton and expensive to move. Delivery and the yard minimum usually matter more than the per-yard rate on a small job — which is why the tool has fields for both, and reports what the load actually costs per yard once you have paid for a minimum you cannot use.
Should I order extra?
A little. Rounded stone rolls off slopes and settles into whatever is underneath, so a bed that looked right on day one usually wants topping up. A small allowance is honest — but nothing published quantifies it, so the waste field starts at zero and it is yours to set rather than something this page decided for you.
Sources
- SOURCE REQUIRED — your supplier's own published density. River rock is a graded decorative product, not a specification aggregate, and its weight per cubic yard moves with the size grade, the roundness and how wet it is. No national figure exists to cite
Awaiting verification against the published data sheet
No density is stored, so no weight is calculated unless the reader supplies one. This is the same treatment sand and pea gravel get on this site and for the same reason: every figure in circulation for decorative river rock traces back to somebody's estimate rather than to a published test. Volume is exact and is always reported; tons are the supplier's number applied to our volume.
Unit conversions are exact by definition and need no source.
How we choose and cite these figures
