Calculator Inputs
Use this tool for raised beds, planter strips, landscape borders, trench fills, and site dressing estimates.
Plotly Graph
The graph shows how adjusted compost volume changes as depth changes for your selected area.
Example Data Table
| Scenario | Inputs | Adjusted Volume | Approx. 40 L Bags |
|---|---|---|---|
| Raised bed | 12 ft × 4 ft × 3 in, 10% waste, 10% settling | 14.52 ft³ / 0.538 yd³ / 411.2 L | 11 bags |
| Circular planter | 8 ft diameter × 2 in, 8% waste, 8% settling | 9.77 ft³ / 0.362 yd³ / 276.7 L | 7 bags |
| Site border strip | 25 m² × 0.05 m, 12% waste, 10% settling | 1.540 m³ / 54.38 ft³ / 1540.0 L | 39 bags |
Formula Used
Area Formulas
Rectangular: Area = Length × Width
Circular: Area = π × (Diameter ÷ 2)²
Triangular: Area = (Base × Height) ÷ 2
Volume Formulas
Raw Volume: Area × Depth
Adjusted Volume: Raw Volume × (1 + Waste%) × (1 + Settling%)
Bags Needed: Ceiling(Adjusted Volume ÷ Bag Volume)
All units are converted internally before calculation, so mixed planning inputs still produce consistent cubic feet, cubic yards, cubic meters, and liters.
How to Use This Calculator
- Select the bed or site shape.
- Enter dimensions using your preferred unit.
- Add the compost depth you want to spread.
- Include waste and settling allowances for safer ordering.
- Set bag size and optional pricing fields.
- Press the calculate button to show results above the form.
- Review the graph, unit conversions, bag count, and cost estimates.
- Download the result as CSV or PDF for project records.
Frequently Asked Questions
1) What depth should I use for compost?
For light top-dressing, many projects use about 1 to 2 inches. For bed improvement or new planting areas, deeper layers are common. Local soil condition and crop needs should guide the final depth.
2) Why add waste and settling allowances?
Compost can compact during transport, raking, watering, and early settlement. A modest allowance helps prevent under-ordering, especially on uneven sites, around edges, and when exact finished depth matters.
3) Should I order by bags or cubic yards?
Small jobs usually fit bag purchasing better. Larger installations often become cheaper and faster with bulk delivery. This calculator shows both approaches so you can compare labor, delivery, and purchasing convenience.
4) Can I use this for mulch or soil blends?
Yes. The volume math is the same for mulch, topsoil, compost blends, and soil conditioners. Only the material type changes, so bag size, settling, and pricing assumptions may need adjustment.
5) Why does depth affect volume so much?
Volume grows directly with depth. If area stays fixed, doubling depth doubles raw material demand. That is why even a small depth change can noticeably raise cost, bag count, and delivery volume.
6) Is cubic meter output useful on construction jobs?
Yes. Many suppliers, drawings, and specifications use metric measures. Showing cubic meters, liters, cubic feet, and cubic yards together makes it easier to compare quotes and site notes without reworking numbers manually.
7) Can I estimate cost with this page?
Yes. Enter a price per bag to estimate packaged material cost. Enter a bulk price per cubic yard to compare delivery-based buying. You can use both fields together for a quick purchasing check.
8) Does shape choice change the final formula?
Only the area formula changes. Once the base area is known, the volume step stays the same: area multiplied by depth, then adjusted for waste and settling allowances.