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River rock mulch chart
Put your bed area, river rock mulch depth and waste allowance in: 3600 sq ft at 3 inches with 10% waste needs 3,960.00 sq ft, 36.67 cubic yards exact — order 37 cubic yards.
★ CONSTRUCTION · MULCH · RIVER ROCK MULCH CHART
River Rock Mulch Chart: 3600 Sq Ft, 3 Inches, Order 37 Yards
On the defaults — a 3600 square foot bed at 3 inches deep with a 10% waste allowance — you need 3,960.00 square feet of cover, 36.67 cubic yards exact, so order 37 cubic yards. This is the RIVER ROCK version — the mulch chart for river rock, which drains fast, stays put on slopes and never breaks down — the sand-mulch-chart page is the SAND version, the pea-gravel-mulch-chart page is the PEA GRAVEL version, and the mulch-chart page is the GENERAL version for any loose mulch.
What does 36.67 cubic yards of river rock mulch mean?
It means a 3600 square foot bed, once the 10% waste allowance is added, needs 3,960.00 square feet of cover at 3 inches deep — 990.00 cubic feet, which is 36.67 cubic yards. Because mulch is sold by the whole yard, you order 37 cubic yards: the extra 0.33 yard covers spillage and the thin spots every bed has. At 3 inches, one cubic yard covers 108.0 square feet, so the same bed at 2 inches would need only 24.44 yards, and at 4 inches it would need 48.89 yards.
Output · formula · meaning
| Output | Formula | What it means |
|---|---|---|
| Area needed | area × (1 + waste ÷ 100) | 3,960.00 sq ft — 3600 × 1.10. |
| Volume in cubic feet | area needed × depth ÷ 12 | 990.00 cubic feet — 3,960.00 × 3 ÷ 12. |
| Exact volume | area needed × depth ÷ 324 | 36.67 cubic yards — 3,960.00 × 3 ÷ 324. |
| Order quantity | round exact volume up to a whole yard | 37 cubic yards — the next whole yard above 36.67. |
| Coverage per yard | 324 ÷ depth | 108.0 sq ft per yard — 324 ÷ 3. |
| Area behind a target volume | target volume × 324 ÷ depth ÷ (1 + waste ÷ 100) | 3600 sq ft — 36.67 × 324 ÷ 3 ÷ 1.10, rounded. |
| Depth behind a target volume | area needed × depth ÷ 324, solved for depth | 3 inches — the depth that turns 3,960.00 sq ft into 36.67 yards. |
| Waste behind a target volume | target volume × 324 ÷ depth ÷ area − 1, as a percent | 10% — the allowance that turns 3600 sq ft into 3,960.00 sq ft. |
Three things to check before you trust the number
First, measure the bed honestly: length times width for each bed, added together, with L-shaped beds split into rectangles. A guessed area moves the order by the same percentage as the guess. Second, keep the depth honest: river rock does not break down, so the layer you spread is the layer that stays — but stones sink into soft soil and wash downhill on slopes, so edge the bed if you want the depth to hold. Third, do not skip the waste allowance on river rock: it is loose and round, so it stays put on flat beds but rolls away on slopes, so the 10% allowance is the difference between finishing the bed and running short with the truck already gone.
Worked example
Area 3600 sq ft, depth 3 inches, waste 10%. Area needed: 3600 × 1.10 = 3,960.00 sq ft. Exact volume: 3,960.00 × 3 ÷ 324 = 36.67 cubic yards. Order: round 36.67 up to 37 cubic yards. Drop the waste to 0% and the exact volume falls to 33.33 yards, order 36; drop the depth to 2 inches and it falls to 24.44 yards, order 26. Depth moves the answer faster than waste does, because every inch adds a full layer across the whole bed.
River rock mulch lookup table
Every row below applies 10% waste to the area first, then divides by 324: yards = area needed × depth ÷ 324, rounded up to the next whole yard for the order. Find your bed size and depth, read across, and order the last column.
| Area (sq ft) | Depth (inches) | Area needed (sq ft, 10% waste) | Exact (cubic yards) | Order |
|---|---|---|---|---|
| 250 | 2 | 275.00 | 1.70 | 2 cubic yards |
| 250 | 3 | 275.00 | 2.55 | 3 cubic yards |
| 500 | 2 | 550.00 | 3.40 | 4 cubic yards |
| 500 | 3 | 550.00 | 5.09 | 6 cubic yards |
| 750 | 2 | 825.00 | 5.09 | 6 cubic yards |
| 750 | 3 | 825.00 | 7.64 | 8 cubic yards |
| 1000 | 2 | 1,100.00 | 6.79 | 7 cubic yards |
| 1000 | 3 | 1,100.00 | 10.19 | 11 cubic yards |
| 1200 | 3 | 1,320.00 | 12.22 | 13 cubic yards |
| 1400 | 2 | 1,540.00 | 9.51 | 10 cubic yards |
| 1500 | 2 | 1,650.00 | 10.19 | 11 cubic yards |
| 1500 | 4 | 1,650.00 | 20.37 | 21 cubic yards |
| 1750 | 3 | 1,925.00 | 17.82 | 18 cubic yards |
| 2000 | 3 | 2,200.00 | 20.37 | 21 cubic yards |
| 2500 | 2 | 2,750.00 | 16.98 | 17 cubic yards |
| 3000 | 3 | 3,300.00 | 30.56 | 31 cubic yards |
Every branch, checked
A 3600 square foot bed at 3-inch depth with 0% waste gives 33.33 cubic yards exact, order 34 cubic yards. The same bed at 2-inch depth with 10% waste gives 24.44 cubic yards exact, order 25 cubic yards. A 3350 square foot bed at 3-inch depth with 10% waste gives 34.12 cubic yards exact, order 35 cubic yards. A 3850 square foot bed at 3-inch depth with 10% waste gives 39.21 cubic yards exact, order 40 cubic yards. Each branch changes exactly one input, so the difference from 36.67 isolates that input.
The reverses, worked backwards
The area behind 36.67 cubic yards is 3600 sq ft: at 3350 sq ft the figures are 34.12 cubic yards exact, order 35 cubic yards, and at 3850 sq ft they are 39.21 cubic yards exact, order 40 cubic yards. The depth behind 36.67 cubic yards is 3 inches: at 2 inches the figures are 24.44 cubic yards exact, order 25 cubic yards, and at 4 inches they are 48.89 cubic yards exact, order 49 cubic yards — one inch either way moves the order by about 12.2 yards. The waste behind 36.67 cubic yards is 10%: at 5% the figures are 35.00 cubic yards exact, order 35 cubic yards, and at 15% they are 38.33 cubic yards exact, order 39 cubic yards — waste moves the exact volume, and at 15% it lifts the order to 39 yards.
What the defaults assume
The defaults assume a flat 3600 square foot bed, a uniform 3-inch layer, and a 10% waste allowance. Real river rock beds are rarely flat: slopes shed stones downhill, paths and tree trunks eat into the area, and loose stones wander into the lawn, so measure the planted area only and keep the waste allowance on sloped ground. Zero square feet is the honest edge: 0.00 cubic yards exact, order 0. A depth of zero or below, a negative area, or a negative waste allowance is rejected, because none of them describes a real bed.
Who uses this
A gardener topping a drainage bed with river rock: the 3600 square foot headline is a large garden bed, and the table covers everything from a 250 square foot border to a 3000 square foot yard. A landscaper quoting a river rock job: the waste column protects the quote, and the order column is the number given to the supplier. A homesteader spreading bulk river rock on paths: the 3-inch rows are the bed depths, and the 2-inch rows are the path depths. A community garden coordinator splitting a bulk delivery: each plot reads its own row, and the orders add up to the truckload.
Accuracy & limitations
The arithmetic is exact for the inputs entered; the judgement is in the inputs. A guessed area, a depth measured before the gravel migrates underfoot, or a skipped waste allowance will each move the answer by exactly the amount of the error, every load. The model does not include gravel migrating into lawns, delivery minimums, or compaction — a supplier may sell only in whole yards or charge extra below a minimum, so confirm the order quantity with the supplier. This page is a calculation tool, not landscaping advice.
Cite this calculator
River rock mulch 3600 sq ft at 3-inch depth with 10% waste needs 3,960.00 sq ft, 36.67 cubic yards exact, order 37 yards. Free calculator, plus 16-row table. Source: Bright Side Kit, https://brightoolbox.com/river-rock-mulch-chart/, accessed 31 October 2026 (2026-10-31).
Frequently asked questions
Why does the table apply waste to the area first?
Because waste is lost cover: spillage, rolling and uneven ground mean you need more covered area than the bed measures. Adding 10% to the area, then converting to yards, keeps the waste in the same units as the bed. Applying it after the conversion gives the same number here, but the area-first order keeps the table readable.
How deep should river rock mulch really be?
Three inches is the standard bed layer on this page, and 2 inches suit paths and top-ups. River rock does not break down, so a 3-inch spread stays 3 inches; if it migrates underfoot, rake it back or top up the thin spots.
Does river rock mulch introduce weed seeds?
River rock is mineral, so it carries no weed seeds at all; weeds can still root in the dust and debris that collects on top of it, so use fabric underneath and clear the debris. This calculator prices volume only and does not judge the gardening choice.
What if my bed is not a rectangle?
Split it into rectangles, measure each, and add the areas before entering the total. A circle uses radius times radius times 3.14. Guessing one number for an irregular bed is the most common reason orders come up short.
Why order 37 yards when the exact figure is 36.67?
Because mulch is sold by the whole yard and you cannot buy 0.33 of a yard from most suppliers. Rounding up also covers spillage and thin spots; the 0.33 yard of headroom is cheaper than a second delivery for a shortfall.
Can I use this chart for other mulch types?
The volume math is the same for any loose mulch — area, depth and waste convert the same way — but settling and coverage differ by material. River rock does not settle like bark, so use the river rock rows for river rock and the matching chart for bark or wood chips.