Calculation Results
Enter one or more garden sections, then select Calculate Soil. Results will appear here above the form.
Formula Used
Circle: V = π × radius² × required depth
Triangle: V = ½ × base × height × required depth
Trapezoid: V = ((side A + side B) ÷ 2) × height × required depth
Ring: V = π × (outer radius² − inner radius²) × required depth
Tapered planter: V = (πh ÷ 3) × (R² + Rr + r²)
The calculator converts every measurement into meters before calculating area and volume. Gross volume uses the selected shape, quantity, and target soil depth. Existing soil, compaction, and waste adjustments are then applied in sequence.
How to Use This Calculator
- Add a garden section and choose its shape.
- Enter dimensions, quantity, desired depth, and current depth.
- Select existing-soil, compaction, and waste settings.
- Choose a soil mix, bag size, and pricing details.
- Select Calculate Soil to view purchase recommendations.
Soil Planning Guide
Accurate soil ordering begins with careful measurements. Measure each garden bed at its longest useful dimensions, then divide irregular gardens into smaller shapes. Adding those sections usually gives a better estimate than treating the whole project as one oversized rectangle.
Depth matters as much as surface area. Lawn topdressing may need only a thin layer, while vegetables and raised beds need considerably more growing medium. Enter current soil depth when topping up an existing bed, because purchasing the full finished volume can create expensive leftovers.
Fresh soil settles after watering, foot traffic, and natural decomposition. A ten percent compaction allowance works for many loose garden mixes, although fluffy compost blends may need more. Waste allowance covers spills, uneven ground, edging gaps, and measurement uncertainty during installation work.
Packaged bags are convenient for small projects and narrow access routes. Bulk soil usually costs less per unit for large gardens, but delivery fees and minimum order increments matter. Compare both totals before purchasing, especially when your calculated amount sits close to a supplier threshold.
A balanced raised-bed mix often combines mineral soil, compost, and an aeration material. The correct recipe depends on drainage, local climate, crop choice, and existing soil. Avoid assuming one universal ratio works for every garden or container.
Planters require special attention because tapered sides change their true volume. Measuring only the widest diameter can overestimate soil needs. This calculator uses a frustum formula for round tapered containers and supports multiple identical pots.
Order recommendations are rounded upward so the project is not left unfinished. The displayed exact volume remains useful for comparing designs and mix components. Keep a small reserve for future settling, transplanting, and minor repairs.
Example Data
| Project | Dimensions | Depth | Approximate volume |
|---|---|---|---|
| Raised bed | 8 ft × 4 ft | 1 ft | 32 ft³ |
| Round flower bed | 6 ft diameter | 0.5 ft | 14.14 ft³ |
| Planter box | 120 cm × 40 cm | 35 cm | 168 L |
Frequently Asked Questions
How much extra soil should I order?
Five to fifteen percent is common. Use more for fluffy mixes, uneven ground, or uncertain measurements.
Should I use current depth or filled percentage?
Use current depth when it can be measured. Filled percentage is useful when only a visual estimate is available.
Does the calculator round bag quantities upward?
Yes. Partial bags are rounded to the next whole bag, then reserve bags are added.
Can I calculate several garden beds together?
Yes. Add, duplicate, edit, or remove sections before calculating the combined total.
What depth should a vegetable bed have?
Many vegetables perform well with 20 to 30 centimeters of usable soil, although deep-rooted crops may need more.
Are mulch and soil calculated the same way?
The volume formula is the same, but mulch layers are usually shallower and may settle differently.
Why compare bags with bulk soil?
Bags suit small jobs, while bulk delivery often reduces unit cost for larger projects.
How does the tapered planter calculation work?
It uses the top radius, bottom radius, and interior height to calculate a round frustum.
Can soil mix ratios use parts?
Yes. Enter values such as 2, 1, and 1. The calculator normalizes them automatically.
Does the cost include delivery and tax?
Yes. Both packaged and bulk estimates can include delivery fees and the entered tax rate.