Landscaping
Garden Soil Calculator
Work out garden soil volume for beds, raised planters or borders.
Result
A common raised-bed mix is roughly 60% topsoil, 30% compost and 10% aeration material. Soil settles after the first few waterings, so fill slightly proud of the final level.
Get a Free Business AuditWhat moves the number
- Bed dimensions including depth, which for raised beds is the full internal depth.
- Whether the bed is filled entirely with soil or partly with a coarser base.
- Soil blend, since compost-heavy mixes settle far more than mineral soil.
Where this one goes wrong
Filling a raised bed entirely with compost-rich mix. It settles dramatically over the first season, leaving the bed half empty, and the customer sees that as a failure of the build rather than a property of the material.
Questions
About this calculator
Why do raised beds sink?
Because organic material decomposes and compacts. A compost-heavy fill can lose a noticeable share of its volume in the first year, which is why beds are often filled proud or topped up the following season.
What should a raised bed be filled with?
A blend rather than pure compost. Mineral content gives structure and holds the level, while organic content provides fertility.
Should the bottom of a deep bed be filled with something else?
For very deep beds it is common to use a coarse base for drainage and volume, which reduces cost. It has to still leave adequate rooting depth for what is being grown.
The formula
cubic yards = length × width × (depth ÷ 12) ÷ 27
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How to use this calculator
- Length (ft) (ft). Enter your own figure; the page starts at 8 ft.
- Width (ft) (ft). Enter your own figure; the page starts at 4 ft.
- Bed depth (inches) (in). Enter your own figure; the page starts at 12 in.
- Waste / compaction allowance (%). Enter your own figure; the page starts at 5%.
- Cost per cubic yard ($). Enter your own figure; the page starts at $48.
- Number of beds. Enter your own figure; the page starts at 3.
The result updates as you type, so you can try a figure, see what it does to cubic yards 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) | 8 ft |
| Width (ft) | 4 ft |
| Bed depth (inches) | 12 in |
| Waste / compaction allowance | 5% |
| Cost per cubic yard | $48 |
| Number of beds | 3 |
What comes out
| Result | Value |
|---|---|
| Cubic yards needed main result | 3.7 |
| Cubic feet | 100.8 |
| Approximate tons | 4.1 |
| Estimated cost | $179.20 |
| 1.5 cu ft bags | 68 |
3 beds need 100.8 cubic feet of soil, 3.7 cubic yards, or 68 bags, costing about $179.20.
How sensitive the answer is
Holding everything else steady and changing only cost per cubic yard, this is what happens to cubic yards needed. It is worth knowing which of your inputs the answer actually hinges on, and which barely move it.
| Cost per cubic yard ($) | Cubic yards needed |
|---|---|
| $24 | 3.7 |
| $36 | 3.7 |
| $48 example above | 3.7 |
| $72 | 3.7 |
| $96 | 3.7 |
Every other input is held at the example value while this one changes, which is not how a real job behaves. Treat it as a guide to which number matters most, not as five separate quotes.
What each figure means
- Length (ft) (ft)
- Measured in ft, starting at 8 ft.
- Width (ft) (ft)
- Measured in ft, starting at 4 ft.
- Bed depth (inches) (in)
- Measured in in, starting at 12 in.
- Waste / compaction allowance (%)
- A percentage, between 0 and 60, starting at 5%.
- Cost per cubic yard ($)
- A money amount, starting at $48.
- Number of beds
- A number, between 0 and 1000, starting at 3.
What the results tell you
| Result | What it is |
|---|---|
| Cubic yards needed | The headline result. A decimal figure. |
| Cubic feet | A decimal figure. |
| Approximate tons | A decimal figure. |
| Estimated cost | A money figure. |
| 1.5 cu ft bags | A number. |
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.
Keep going
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