River Rock Calculator: The Depth Is Half the Order
Enter your project dimensions
Walk out to the bed you are about to redo and look at what is showing. Fabric through the stone, soil between the pieces, a border gone thin along the front edge: those are the things a Maryland reader can actually measure, and each one points at a different number going into the river rock calculator. Get the depth wrong and no amount of stone fixes the look, because coverage on rounded stone is set by how thick the layer is against how big the pieces are.
Three ways a river rock order lands short before the truck is booked
The bed was measured, the layer was guessed at. Rounded stone hides the ground when the layer runs to roughly twice the diameter of the pieces. Three-inch stone raked out two inches deep leaves gaps you can see into, and the answer is a deeper layer rather than a bigger delivery. Set the depth first, then measure.
A ton looks smaller tipped out than it does on paper. At the weight this site publishes for the material, a single ton is about three quarters of a cubic yard. People who order by eye after reading the figure on screen are usually the ones who come up short.
An old bed was measured as though it were bare ground. Topping up a settled bed is a thin job. If the existing stone is already two inches deep and you want three, the depth that goes in the form is one inch, not three.
Feeding a creek bed and four splash aprons into one run
The form opens on a shape. Rectangle takes a length and a width in feet, which covers most borders and beds. Circle asks for a diameter in feet, measured straight across the widest point of a ring or a round planting bed. Multiple areas holds up to five separate pieces in one calculation, which is what a garden with a creek bed and a run of downspout aprons really is.
Depth goes in as inches and the box accepts anything from 0.25 up to 24. Pick the material next, because that selection is what sets the weight the tool converts with. The box marked add 5 percent extra for compaction and spillage is worth ticking on anything that will be wheelbarrowed across grass or raked hard against an edge. Press calculate and three figures come back at once. The result can be emailed across as a written quote instead of being copied off the screen onto the back of an envelope.
Cubic yards for the bed, tons for the order, cubic feet for the wheelbarrow
Volume is what the bed takes. Weight is what the listing sells. The cubic yard number tells you whether a bed and a border can share one delivery; the ton number is what goes in the quantity box; the cubic feet figure is the one to keep if the job is small enough to move by hand, since a builder's wheelbarrow holds around three of them.
Doing it yourself takes three moves. Length times width gives the area in square feet. The depth in inches becomes feet when you divide it by twelve, and multiplying the two together gives cubic feet. Twenty-seven of those make a cubic yard, so divide, then multiply the yards by the weight figure for the stone you picked.
Rounded stone by size, and where each one ends up on a Maryland lot
| Stone size | Where it usually goes here | Layer to plan for |
|---|---|---|
| 3/4 to 1 inch River Rock | Borders and narrow strips along a path or a foundation | 2 inches |
| 1 to 3 inch River Rock | Beds, downspout aprons, edges that take roof water | 3 to 4 inches |
| Large River Rock at 2 to 4 inch | Dry creek beds and heavier decorative work on a slope | 4 to 5 inches |
| Drain Rock where the bed is carrying water | French drains, drywells and foundation runs | The full trench depth |
River rock in the 1 to 3 inch range is published here at roughly 2,700 lb for every cubic yard, which works out at 1.35 tons, and that is an approximate figure rather than a weighbridge reading. Anything with the word drain in front of it is a different job and belongs on the stone calculator, where the clean washed grades sit.
Non-woven fabric goes down before decorative stone, pinned, with the rock spread over it. Where the stone is doing drainage work instead, wrap the fabric around the stone rather than laying it flat underneath.
A Piedmont creek bed and a border on a Shore lot, measured through
Both of these are invented for this page rather than jobs anyone has ordered.
A dry creek bed, 28 feet long and averaging 5 feet wide, in Large River Rock at 5 inches. The area is 140 square feet. Five inches is 0.4167 of a foot, so the volume comes to 58.3 cubic feet, which divides down to 2.16 cubic yards. At 1.35 tons to the yard that is about 2.9 tons, and with the 5 percent box ticked it reads 2.27 cubic yards, near enough 3.1 tons. Order 3 tons and sink the biggest anchor pieces a third of their height into the ground.
A border on a Bay-side lot, 44 feet by 2.5 feet, in 1 to 3 inch stone at 3 inches. That is 110 square feet at a quarter of a foot, so 27.5 cubic feet, or 1.02 cubic yards, or roughly 1.4 tons. Keep the surplus for the front edge, which is always the first strip to thin out.
Before either of those goes in on a waterfront lot, check the Critical Area. Within 1,000 feet of tidal waters and tidal wetlands, lot coverage is capped, and gravel, stone and pavers all count toward that cap. The figure and the detail come from the county Critical Area program rather than from one statewide percentage, so a new bed near the shoreline is a permitting question before it is a tonnage question.
Where three tons of rounded stone should be tipped
Rounded stone rolls, which makes the drop spot worth choosing in advance. Firm ground, nothing overhead, room for a truck to back in and tip, and a tarp underneath if the pile has to land on a drive or an apron. Uphill of the bed beats downhill of it every time. Once the tonnage is settled, set the quantity on the product listing and choose a date there; delivery is arranged at checkout by ZIP code, and the delivery page covers what the driver needs at the far end. Give the finished bed a rinse with a hose, since dust off the load mutes the color until it is washed. Bark over a planted bed and 3/8 inch rounded stone on a path are different weights again, sized on the mulch calculator and the pea gravel calculator.
Common questions
The bed is still half full of old stone. What do I put in the depth box?
The difference, not the finished depth. Push a trowel down through the existing rock in three or four spots to find what is really there, average it, and subtract that from the depth you want. A bed sitting at two inches that needs to read four goes into the form as two. On a bed that has gone patchy rather than evenly thin, rake the stone level first and measure afterwards, because the average of a lumpy bed is not a number you can order against.
What actually goes wrong if the order comes up half a ton light?
You finish the bed thin rather than short, which is the worse of the two outcomes: a thin layer lets fabric and soil show through and it does not improve with time. The usual repair is a second small delivery for one bed, and hauling a part load is rarely worth doing twice. Round the calculated figure up to the next whole ton and put the surplus along the visible front edge.
How close is the figure to what the bed will really take?
Close on a flat bed with square edges, less so on a curved one, and it is the depth and the ground that move it rather than the arithmetic. Rounded stone settles into soft soil unless fabric goes down first, which is why a bed laid straight on bare earth seems to swallow rock in its second year. Measure carefully, enter the real depth, and treat the result as a good estimate rather than an exact count.
I have the tonnage. Which listing do I open to buy it?
River Rock for the smaller graded sizes, Large River Rock for the 2 to 4 inch material, or Drain Rock if the bed is really a drainage run with stone on top. All three are ordered by the ton, so the number from the form carries straight into the quantity box. Set the delivery date on the same page.
The only firm ground is out front and the bed is out back. How do I plan the drop?
Work out the wheelbarrow count before the day rather than on it. Three tons of this material is a little over two cubic yards, which is somewhere near twenty full wheelbarrow loads, so the route matters more than the distance. Lay boards across soft lawn, pick the shortest line from a firm tipping spot, and where the ground slopes, have the pile put at the top so the loaded trips run downhill.
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