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River rock chart calculator
Put your area, depth and waste allowance in: 400 square feet at 2 inches with 10% waste needs 440.00 square feet, 2.72 cubic yards exact, order 3 cubic yards.
★ CONSTRUCTION · MATERIALS · RIVER ROCK CHART
River Rock Chart: 3 Cubic Yards for 400 Sq Ft at 2 Inches
On the defaults — 400 square feet at 2-inch depth with 10% waste — you need 440.00 square feet of coverage, which is 2.72 cubic yards exact, so order 3 cubic yards. This is the RIVER ROCK version of the coverage chart — the crushed-stone-chart page is the CRUSHED STONE version — 400 square feet at 2 inches with 10% waste; the pea-gravel-chart page is the PEA GRAVEL version — 300 square feet at 3 inches with 10% waste; the mulch-chart page is the MULCH version — 400 square feet at 3 inches; and the topsoil-chart page is the TOPSOIL version — 400 square feet at 10% waste.
River rock chart
One cubic yard of river rock covers 324 square feet at 1 inch deep, 162 square feet at 2 inches, 108 square feet at 3 inches, and 81 square feet at 4 inches — because a cubic yard is 27 cubic feet, and 27 cubic feet spread 1 inch deep covers 324 square feet. The lookup table below already includes 10% waste, so read your area and depth straight off it; the calculator above handles any other area, depth, or waste figure. The order column rounds up to whole cubic yards, because river rock is delivered by the yard and a part-yard shortfall leaves the job unfinished.
What does 2.72 cubic yards of river rock mean?
It means that 400 square feet at 2 inches deep needs 440.00 square feet of coverage once 10% waste is added, and 440.00 divided by 162 square feet per cubic yard is 2.72 cubic yards exact — so you order 3 whole cubic yards and keep the leftover 0.28 yard for touch-ups. The two steps are the whole story in miniature: the waste factor turns the measured area into the area you must actually cover, and the coverage figure turns that area into cubic yards. The part people get wrong is ordering the exact figure: 2.72 cubic yards cannot be delivered as 2.72, and rounding down to 2 leaves 0.72 yard — about 117 square feet at 2 inches — uncovered. The other part people get wrong is the reverse — forgetting waste entirely, which understates the order by 0.25 yard on this job and by a full yard on a big one.
Three things to check before you trust the number
Is 400 square feet really the area, or the area plus edges? Four hundred square feet is the measured ground the river rock covers, and it is the figure the needed area turns on: the 600-square-foot branch needs 4.07 cubic yards exact against the 2.72 headline, so a 200-square-foot measuring difference is 1.35 yards. Measure length times width for each section and add the sections; a guess at the area is a guess at the order.
Is 2 inches really the depth, or the depth after raking level? Two inches is the finished depth, and it is the figure the coverage turns on: the 4-inch branch needs 5.43 cubic yards exact against the 2.72 headline, so two extra inches nearly doubles the order. Smooth rounded river rock shifts underfoot and washes in heavy rain, so a bed that must finish at 2 inches after raking level needs the full depth spread evenly — measure the finished depth you need, not the depth tipped from the barrow. Lay weed barrier underneath first, or soil works up through the rock and the bed thins from below.
Is 10% really enough waste? Ten percent is the allowance for spreading loss, uneven ground, and edging gaps, and it is the figure the needed area turns on: the 0%-waste branch needs 2.47 cubic yards exact against the 2.72 headline, so the waste allowance alone is 0.25 yard on this job. Uneven ground, a long wheelbarrow haul, or rock rolling off the bed edges all eat river rock; a flat, measured, edged area is the only job where 0% is honest.
Worked example
On the defaults: 400 square feet, 2-inch depth, 10% waste.
- Coverage per cubic yard: 324 ÷ 2 is 162 square feet.
- Needed area: 400 × 1.10 is 440.00 square feet.
- Exact cubic yards: 440.00 ÷ 162 is 2.72 cubic yards.
- Order: 2.72 rounded up is 3 cubic yards.
And the other way: the area behind 2.72 cubic yards is 400 square feet, the depth behind 2.72 cubic yards is 2 inches, and the waste behind 2.72 cubic yards is 10%. With 0 square feet the model honestly shows 0.00 cubic yards exact and an order of 0, because an area of nothing needs no river rock — an edge that shows the area is entered independently of the depth.
River Rock lookup table (10% waste included)
| Area (sq ft) | Depth (inches) | Needed area (sq ft) | Exact cubic yards | Order |
|---|---|---|---|---|
| 150 | 1 | 165.00 | 0.51 | 1 cubic yard |
| 150 | 2 | 165.00 | 1.02 | 2 cubic yards |
| 150 | 3 | 165.00 | 1.53 | 2 cubic yards |
| 150 | 4 | 165.00 | 2.04 | 3 cubic yards |
| 300 | 1 | 330.00 | 1.02 | 2 cubic yards |
| 300 | 2 | 330.00 | 2.04 | 3 cubic yards |
| 300 | 3 | 330.00 | 3.06 | 4 cubic yards |
| 300 | 4 | 330.00 | 4.07 | 5 cubic yards |
| 450 | 1 | 495.00 | 1.53 | 2 cubic yards |
| 450 | 2 | 495.00 | 3.06 | 4 cubic yards |
| 450 | 3 | 495.00 | 4.58 | 5 cubic yards |
| 450 | 4 | 495.00 | 6.11 | 7 cubic yards |
| 600 | 1 | 660.00 | 2.04 | 3 cubic yards |
| 600 | 2 | 660.00 | 4.07 | 5 cubic yards |
| 600 | 3 | 660.00 | 6.11 | 7 cubic yards |
| 600 | 4 | 660.00 | 8.15 | 9 cubic yards |
Every branch, checked
- 400 square feet, 2-inch depth, 0% waste: 400 square feet, 2-inch depth, 0% waste: 2.47 cubic yards exact — order 3 cubic yards.
- 400 square feet, 4-inch depth, 10% waste: 400 square feet, 4-inch depth, 10% waste: 5.43 cubic yards exact — order 6 cubic yards.
- 600 square feet, 2-inch depth, 10% waste: 600 square feet, 2-inch depth, 10% waste: 4.07 cubic yards exact — order 5 cubic yards.
- 200 square feet, 2-inch depth, 10% waste: 200 square feet, 2-inch depth, 10% waste: 1.36 cubic yards exact — order 2 cubic yards.
The reverses, worked backwards
- Area behind 2.72 cubic yards: 400 sq ft — at 400 sq ft the figures are 2.72 cubic yards exact — order 3 cubic yards.; at the lower neighbor the figures are 2.38 cubic yards exact — order 3 cubic yards.; at the upper neighbor the figures are 3.06 cubic yards exact — order 4 cubic yards..
- Depth behind 2.72 cubic yards: 2 inches — at 2 inches the figures are 2.72 cubic yards exact — order 3 cubic yards.; at the lower neighbor the figures are 2.04 cubic yards exact — order 3 cubic yards.; at the upper neighbor the figures are 3.40 cubic yards exact — order 4 cubic yards..
- Waste behind 2.72 cubic yards: 10% waste — at 10% waste the figures are 2.72 cubic yards exact — order 3 cubic yards.; at the lower neighbor the figures are 2.59 cubic yards exact — order 3 cubic yards.; at the upper neighbor the figures are 2.84 cubic yards exact — order 3 cubic yards..
What the defaults assume
The defaults are 400 square feet at 2-inch depth with 10% waste, so the headline is one smooth river-rock bed over a modest area. The model is a multiplication and a division: the needed area is area times the waste factor, the coverage per cubic yard is 324 divided by depth in inches, and the exact figure is needed area divided by coverage, rounded up to order. The area reverse is checked at 50 square feet either side, because 50 square feet at 2 inches with 10% waste is 0.34 yard; the depth reverse is checked at 0.5 inches either side, because half an inch either way moves the coverage by a wide margin at shallow depths; the waste reverse is checked at 5% either side, because 5% of 400 square feet is 20 square feet, or 0.12 yard. The model does not include rock size, moisture weight, or delivery minimums — a supplier may round an order of 3 cubic yards up to a minimum load, and wet rock weighs far more than dry rock per yard.
Output · formula · meaning
| Output | Formula | What it means |
|---|---|---|
| Coverage per cubic yard | 324 ÷ depth in inches | 162 sq ft — 324 ÷ 2. |
| Needed area | area × (1 + waste ÷ 100) | 440.00 sq ft — 400 × 1.10. |
| Exact cubic yards | needed area ÷ coverage per cubic yard | 2.72 — 440.00 ÷ 162. |
| Order | exact cubic yards rounded up | 3 cubic yards — 2.72 rounded up. |
| Area behind a target exact figure | target exact × coverage ÷ (1 + waste ÷ 100) | 400 sq ft — 2.72 × 162 ÷ 1.10, approximately. |
| Depth behind a target exact figure | 324 ÷ (needed area ÷ target exact) | 2 inches — 324 ÷ (440.00 ÷ 2.72), approximately. |
| Waste behind a target exact figure | (target exact × coverage ÷ area − 1) × 100 | 10% — (2.72 × 162 ÷ 400 − 1) × 100, approximately. |
| 400 square feet, 2-inch depth, 0% waste | same model | 2.47 cubic yards exact — order 3 cubic yards. |
| 400 square feet, 4-inch depth, 10% waste | same model | 5.43 cubic yards exact — order 6 cubic yards. |
| 600 square feet, 2-inch depth, 10% waste | same model | 4.07 cubic yards exact — order 5 cubic yards. |
| 200 square feet, 2-inch depth, 10% waste | same model | 1.36 cubic yards exact — order 2 cubic yards. |
| Area behind 2.72 cubic yards | reverse | 400 sq ft: 2.72 cubic yards exact — order 3 cubic yards. |
| Depth behind 2.72 cubic yards | reverse | 2 inches: 2.72 cubic yards exact — order 3 cubic yards. |
| Waste behind 2.72 cubic yards | reverse | 10% waste: 2.72 cubic yards exact — order 3 cubic yards. |
| 0 square feet | same model | 0.00 cubic yards exact — order 0 cubic yards. |
| Negative area | same model | Area — 0 or more. |
| Zero depth | same model | Depth — more than 0. |
| 162 square feet, 0% waste | same model | 1.00 cubic yards exact — order 1 cubic yard. |
Who uses this
- A homeowner dressing a landscaping bed — 400 square feet at 2 inches is 2.72 cubic yards exact, with the table showing what a deeper bed or a bigger area costs before the order is placed.
- A landscaper quoting a river rock job — the branches price a deeper layer or a larger area at once, so a quote change can be costed before it is agreed.
- A gardener topping up a drainage run — the reverses recover the area, the depth, or the waste behind any quoted yardage, so a supplier quote can be checked line by line.
- A DIYer topping up a river rock bed — the lookup table reads straight off for small areas, so a top-up can be ordered without running the calculator.
Accuracy & limitations
Figures are the model’s own arithmetic on the numbers you type, computed from unrounded values and displayed rounded HALF_UP to 2dp. The main limitation is the inputs, not the arithmetic: whether the area is measured honestly, whether the depth is the finished depth after raking level, and whether the waste allowance fits the ground are all judgement calls, and this page prices the figures you enter without checking them. River rock size, moisture, and supplier minimum loads are outside the model. This page is a calculation tool, not construction advice.
Cite this calculator
400 square feet at 2-inch depth and 10% waste: 440.00 square feet, 2.72 cubic yards exact, order 3 cubic yards. Source: Bright Side Kit, https://brightoolbox.com/river-rock-chart/, accessed 29 October 2026.
Frequently asked questions
Why does one cubic yard cover 324 square feet at 1 inch?
Because a cubic yard is 27 cubic feet, and 27 cubic feet spread 1 inch deep covers 324 square feet: 27 divided by one twelfth of a foot is 324. At 2 inches the same yard covers half that, 162 square feet, and at 4 inches a quarter, 81 square feet.
Should I order the exact figure or round up?
Round up: river rock is delivered by the whole yard, and rounding 2.72 down to 2 leaves about 117 square feet at 2 inches uncovered. The leftover from rounding up is useful for touch-ups, levelling dips, and settling.
What waste allowance should I use?
Ten percent suits most jobs: spreading loss, uneven ground, and edging gaps all eat river rock. Use 0% only for a flat, carefully measured area, and consider more than 10% for rough ground or a long haul.
Does river rock type change the calculation?
Not the volume: a cubic yard is a cubic yard whatever the rock. Size changes weight, drainage, and price — small river rock, medium river rock, and large river rock all cover the same area per yard but behave differently once laid.
How do I measure an irregular area?
Split it into rectangles and triangles, measure length times width for each, and add the sections. A rough outline guessed as one rectangle usually overstates or understates the area by more than the waste allowance covers.
Why does depth matter so much?
Because coverage is inversely proportional to depth: doubling the depth halves the coverage per yard, so a 2-inch layer needs twice the river rock of a 1-inch layer over the same area. Check the finished depth after raking level, not just the depth tipped from the barrow.