Landscaping
Landscaping Rock Coverage Calculator
Work out decorative rock quantity from area, depth and stone size.
Result
Coverage depends on stone size and depth. Smaller stone covers more ground per ton than larger, and at two inches deep a ton of 3/4 inch rock covers roughly 80 to 100 square feet. Coverage figures on a bag or a box are laboratory numbers measured on a flat, prepared surface. Real surfaces are rougher, more absorbent and more awkward than that, so the honest allowance is always higher than the label suggests.
Get a Free Business AuditWhat moves the number
- Stone size, since larger stone needs more depth to cover the ground properly.
- Area, measured to the bed edge rather than estimated.
- Whether the rock is going over membrane or straight onto soil.
Where this one goes wrong
Using the same depth for large stone as for small. Larger decorative stone needs a deeper layer to sit stably and to hide what is beneath it, and a depth suited to pea gravel leaves large stone looking sparse.
Questions
About this calculator
Does stone size change the quantity?
Yes, because the layer has to be deep enough to cover. Larger stone needs more depth for the same visual result, which means more material for the same area.
Should rock go over membrane?
Usually. It slows weed growth and keeps the stone from working down into the soil, which is what makes a rock bed look tired after a few years.
Is decorative rock low maintenance?
Lower than planting but not zero. Leaves and debris collect in it and weeds establish in that debris, so it needs clearing rather than ignoring.
The formula
tons = area / coverage per ton
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How to use this calculator
- Length (ft) (ft). Enter your own figure; the page starts at 30 ft.
- Width (ft) (ft). Enter your own figure; the page starts at 8 ft.
- Coverage per ton (sq ft) (sq ft). Enter your own figure; the page starts at 80 sq ft.
- Waste allowance (%). Extra for cuts, breakage and offcuts.
- Cost per ton ($). Enter your own figure; the page starts at $95.
The result updates as you type, so you can try a figure, see what it does to tons needed, and change it back. Nothing you enter is sent anywhere or saved.
A worked example
These are the figures the calculator opens with. Every number in the results column below is produced by the same calculation the page runs, so you can follow it through before putting your own figures in.
What goes in
| Input | Value |
|---|---|
| Length (ft) | 30 ft |
| Width (ft) | 8 ft |
| Coverage per ton (sq ft) | 80 sq ft |
| Waste allowance | 8% |
| Cost per ton | $95 |
What comes out
| Result | Value |
|---|---|
| Tons needed main result | 4 |
| Area | 240.0 |
| Area including waste | 259.2 |
| Estimated material cost | $380 |
For 240.0 sq ft plus 8% waste you need 4 tons, costing about $380.
How sensitive the answer is
Holding everything else steady and changing only cost per ton, this is what happens to tons needed. It is worth knowing which of your inputs the answer actually hinges on, and which barely move it.
| Cost per ton ($) | Tons needed |
|---|---|
| $47.5 | 4 |
| $71.25 | 4 |
| $95 example above | 4 |
| $142.5 | 4 |
| $190 | 4 |
Every other input is held at the example value while this one changes, which is not how a real job behaves. Treat it as a guide to which number matters most, not as five separate quotes.
What each figure means
- Length (ft) (ft)
- Measured in ft, starting at 30 ft.
- Width (ft) (ft)
- Measured in ft, starting at 8 ft.
- Coverage per ton (sq ft) (sq ft)
- Measured in sq ft, starting at 80 sq ft.
- Waste allowance (%)
- Extra for cuts, breakage and offcuts.
- Cost per ton ($)
- A money amount, starting at $95.
What the results tell you
| Result | What it is |
|---|---|
| Tons needed | The headline result. A number. |
| Area | A decimal figure. |
| Area including waste | A decimal figure. |
| Estimated material cost | A money figure. |
Seasonality is not in this
Coverage and material figures assume the area you enter. Slope, access for machinery, existing growth and the time of year all affect both quantity and labour, and none of them appear in a calculation like this.
Estimating is the easy part
The jobs you never hear about cost more than the ones you mis-measure. BDEVY builds the marketing, systems and automation that bring them in.