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Volcanic rock chip chart calculator
Put your area, depth and waste allowance in: 650 sq ft at 3 inches with 10% waste needs 715.00 sq ft, 6.62 cubic yards exact — order 7 yards.
★ CONSTRUCTION · GARDEN · VOLCANIC ROCK CHIP CHART
Volcanic Rock Chip Chart: 650 Sq Ft, 3 Inches, 7 Yards
On the defaults — 650 square feet of volcanic rock chips at 3 inches deep with 10% waste — you need 715.00 square feet of cover, 6.62 cubic yards exact, so order 7 cubic yards. This is reference table #446 — the crushed-glass-chip-chart page is table #444 — 750 square feet at 3 inches with 10% waste; the quartz-chip-chart page is table #443 — 900 square feet at 3 inches with 10% waste; the basalt-chip-chart page is the basalt version; and the construction hub collects the whole chip-chart library.
What does 6.62 cubic yards of volcanic rock chips mean?
It means that a 650-square-foot bed at 3 inches deep, with 10% allowed for waste, needs 715.00 square feet of cover, which works out to 6.62 cubic yards before rounding — and since chips are ordered by the whole yard, you order 7. The three numbers are the whole story in miniature: the waste allowance lifts the measured area to the area you actually have to cover, the depth turns that area into a volume, and the rounding turns an exact volume into an order you can place. The part people get wrong is ordering the exact figure: 6.62 cubic yards cannot be delivered as 6.62, so ordering 6 leaves the bed short, and the shortfall shows up at the far end of the bed where it is hardest to fix. The other part people get wrong is skipping the waste allowance: a 650-square-foot bed ordered without it is 6.02 cubic yards, and the missing 0.60 cubic yards is exactly the spillage and edge trimming the allowance exists to cover.
Three things to check before you trust the number
Is 650 square feet really the bed? Six hundred fifty square feet is the measured area, and it is the figure the whole calculation turns on: the 1000-square-foot branch orders 11 yards against the 7-yard headline, so a 350-square-foot measuring difference is 4 whole yards. Measure at the widest points, split irregular beds into sections and add them, and re-measure after edging is set — edging moves the boundary and the boundary moves the area.
Is 3 inches really the finished depth? Three inches is the settled layer, and it is the figure the volume turns on: the 2-inch branch orders 5 yards against the 7-yard headline, so a 1-inch depth difference is 2 whole yards. Chips settle and spread under foot traffic, so set the depth after compaction, not from the loose pile — a loose 3 inches that settles to 2 leaves the bed thin within a season.
Is 10% really the right waste allowance? Ten percent is the middle allowance, and it is the figure the needed area turns on: the 0%-waste branch orders 7 yards against the 7-yard headline here, so the allowance alone does not change the order at this size — but the 15% branch also orders 7, which shows rounding can hide a real volume difference. A tidy flat bed can run 5%, while a sloped bed, a bed with many edges, or a first-time spreader may need 15% — check your own size in the calculator before deciding.
Worked example
On the defaults: 650 square feet, 3-inch depth, 10% waste.
- Needed area: 650 × 1.10 is 715.00 sq ft.
- Coverage per cubic yard: 324 ÷ 3 is 108 sq ft.
- Exact cubic yards: 715.00 × 3 ÷ 324 is 6.62.
- Order: 6.62 rounded up is 7 cubic yards — the exact figure plus the rounding to a whole deliverable yard.
And the other way: the area behind 6.62 cubic yards is 650 square feet, the depth behind it is 3 inches, and the waste behind it is 10%. With 324 square feet at 0% waste the model honestly shows 3.00 cubic yards exact and an order of 3 — the one case where the exact figure is already whole, so rounding changes nothing.
Volcanic rock chip lookup table
Every row below is the same formula at 10% waste: needed area is area × 1.10, exact cubic yards are needed area × depth ÷ 324, and the order is the exact figure rounded up. Find your area row and depth column, or use the calculator above for any size the table does not list.
| Area (sq ft) | Depth (inches) | Needed area (sq ft) | Exact cubic yards | Order |
|---|---|---|---|---|
| 400 | 2 | 440.00 | 2.72 | 3 cubic yards |
| 400 | 3 | 440.00 | 4.07 | 5 cubic yards |
| 400 | 4 | 440.00 | 5.43 | 6 cubic yards |
| 400 | 6 | 440.00 | 8.15 | 9 cubic yards |
| 650 | 2 | 715.00 | 4.41 | 5 cubic yards |
| 650 | 3 | 715.00 | 6.62 | 7 cubic yards |
| 650 | 4 | 715.00 | 8.83 | 9 cubic yards |
| 650 | 6 | 715.00 | 13.24 | 14 cubic yards |
| 900 | 2 | 990.00 | 6.11 | 7 cubic yards |
| 900 | 3 | 990.00 | 9.17 | 10 cubic yards |
| 900 | 4 | 990.00 | 12.22 | 13 cubic yards |
| 900 | 6 | 990.00 | 18.33 | 19 cubic yards |
| 1200 | 2 | 1,320.00 | 8.15 | 9 cubic yards |
| 1200 | 3 | 1,320.00 | 12.22 | 13 cubic yards |
| 1200 | 4 | 1,320.00 | 16.30 | 17 cubic yards |
| 1200 | 6 | 1,320.00 | 24.44 | 25 cubic yards |
Every branch, checked
- 650 square feet, 3-inch depth, 0% waste: 650 square feet, 3-inch depth, 0% waste: 6.02 cubic yards exact — order 7 cubic yards.
- 650 square feet, 2-inch depth, 10% waste: 650 square feet, 2-inch depth, 10% waste: 4.41 cubic yards exact — order 5 cubic yards.
- 1000 square feet, 3-inch depth, 10% waste: 1000 square feet, 3-inch depth, 10% waste: 10.19 cubic yards exact — order 11 cubic yards.
- 400 square feet, 3-inch depth, 10% waste: 400 square feet, 3-inch depth, 10% waste: 4.07 cubic yards exact — order 5 cubic yards.
The reverses, worked backwards
- Area behind 6.62 cubic yards: 650 sq ft — at 650 sq ft the figures are 6.62 cubic yards exact — order 7 cubic yards.; at the lower neighbor the figures are 6.11 cubic yards exact — order 7 cubic yards.; at the upper neighbor the figures are 7.13 cubic yards exact — order 8 cubic yards..
- Depth behind 6.62 cubic yards: 3 inches — at 3 inches the figures are 6.62 cubic yards exact — order 7 cubic yards.; at the lower neighbor the figures are 5.52 cubic yards exact — order 6 cubic yards.; at the upper neighbor the figures are 7.72 cubic yards exact — order 8 cubic yards..
- Waste behind 6.62 cubic yards: 10% waste — at 10% waste the figures are 6.62 cubic yards exact — order 7 cubic yards.; at the lower neighbor the figures are 6.32 cubic yards exact — order 7 cubic yards.; at the upper neighbor the figures are 6.92 cubic yards exact — order 7 cubic yards..
What the defaults assume
The defaults are 650 square feet, 3-inch depth and 10% waste, so the headline is one medium garden bed dressed with volcanic rock chips at a standard mulch depth. The model is a multiplication, a division and a rounding up: the needed area is area times one plus waste over 100, the exact volume is needed area times depth divided by 324 — the constant that converts square feet times inches into cubic yards — and the order is that volume rounded up to the next whole yard. The area reverse is checked at 50 square feet either side, because 50 square feet at 3 inches is about 0.46 cubic yards; the depth reverse is checked at 0.5 inches either side, because half an inch over 715 square feet is about 1.10 cubic yards; the waste reverse is checked at 5% either side, because 5% of 650 square feet at 3 inches is about 0.30 cubic yards. The model does not include delivery minimums, the weight of the load, or any base layer under the chips — price those separately, and re-check the order when the bed size or the depth changes.
Output · formula · meaning
| Output | Formula | What it means |
|---|---|---|
| Needed area | area × (1 + waste ÷ 100) | 715.00 sq ft — 650 × 1.10. |
| Coverage per cubic yard | 324 ÷ depth in inches | 108 sq ft — 324 ÷ 3. |
| Exact cubic yards | needed area × depth ÷ 324 | 6.62 — 715.00 × 3 ÷ 324. |
| Order | exact cubic yards, rounded up | 7 cubic yards — 6.62 rounded up. |
| 650 square feet, 3-inch depth, 0% waste | same model | 6.02 cubic yards exact — order 7 cubic yards. |
| 650 square feet, 2-inch depth, 10% waste | same model | 4.41 cubic yards exact — order 5 cubic yards. |
| 1000 square feet, 3-inch depth, 10% waste | same model | 10.19 cubic yards exact — order 11 cubic yards. |
| 400 square feet, 3-inch depth, 10% waste | same model | 4.07 cubic yards exact — order 5 cubic yards. |
| Area behind 6.62 cubic yards | reverse | 650 sq ft: 6.62 cubic yards exact — order 7 cubic yards. |
| Depth behind 6.62 cubic yards | reverse | 3 inches: 6.62 cubic yards exact — order 7 cubic yards. |
| Waste behind 6.62 cubic yards | reverse | 10% waste: 6.62 cubic yards exact — order 7 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. |
| Negative waste | same model | Waste allowance — 0 or more. |
| 324 square feet, 0% waste | same model | 3.00 cubic yards exact — order 3 cubic yards. |
Who uses this
- A gardener dressing a bed with volcanic rock chips — 650 square feet at 3 inches is 7 yards ordered, with the lookup table covering the common bed sizes at a glance before the calculator is touched.
- A landscaper quoting a chip job — the branches price a larger bed or a thinner layer at once, so a quote can be adjusted on site without redoing the arithmetic.
- A homeowner checking a delivery ticket — the reverses recover the area, depth or waste behind any quoted yardage, so a short delivery can be spotted against the measured bed.
- A garden center clerk answering a coverage question — the coverage figure of 108 square feet per cubic yard at 3 inches converts any bed size into yards in one division.
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, with the order rounded up to the next whole yard. The main limitation is the inputs, not the arithmetic: whether the area is measured at the widest points, whether the depth is the settled layer, and whether the waste allowance fits the ground are all judgement calls, and this page prices the figures you enter without checking them. This page is a calculation tool, not landscaping advice.
Cite this calculator
650 sq ft of volcanic rock chips at 3 inches with 10% waste needs 715.00 sq ft: 6.62 cubic yards exact, order 7 yards. Source: Bright Side Kit, https://brightoolbox.com/volcanic-rock-chip-chart/, accessed 29 October 2026.
Frequently asked questions
Why 324 in the formula?
Because a cubic yard is 27 cubic feet, and a square foot times an inch is one twelfth of a cubic foot: 27 × 12 is 324, so area in square feet times depth in inches divided by 324 gives cubic yards directly. The constant is unit conversion, not a property of volcanic rock.
Why round up instead of rounding to nearest?
Because a short bed cannot be finished with a fraction of a delivery: 6.62 yards ordered as 6 leaves 0.62 yards of bed bare, while ordering 7 leaves a small surplus that tops up thin spots. Rounding up is the only direction that never leaves the job unfinished.
What if my bed is an irregular shape?
Split it into rectangles and triangles, measure each section, and add the sections for the total area — then enter that total. A single guessed rectangle over an irregular bed is the most common cause of a short order.
Is the settled depth or the loose depth the right input?
The settled depth: chips compact under foot traffic and weather, so a loose 3-inch spread that settles to 2 inches leaves the bed thin. Measure the depth you want after the chips have settled, and enter that.
How much waste should I allow?
10% is the middle default: 5% suits a tidy flat bed, 15% suits a sloped bed, a bed with many edges, or a first-time spreader. On these defaults 15% orders 7 yards, so the extra allowance costs no whole yard here — check your own size in the calculator before deciding.
Does volcanic rock weigh more than mulch?
Yes, and the model does not price weight: volcanic rock is far denser than bark mulch, so the same 7 cubic yards is a much heavier load. Check the supplier's weight limits and delivery terms separately before ordering.