Calculator
Pick a planter shape, choose units, and calculate soil needs.
Layout: 3 inputs on large, 2 on medium, 1 on small.
Example data table
| Planter type | Dimensions | Fill (%) | Drainage | Estimated soil (L) |
|---|---|---|---|---|
| Rectangular | 60×25×25 cm | 90 | 3 cm | 33.8 |
| Round | Diameter 30 cm, Height 28 cm | 95 | 2 cm | 18.9 |
| Tapered round | Top 36 cm, Bottom 24 cm, Height 30 cm | 90 | 4 cm | 20.7 |
These are illustrative values. Your results change with inside measurements and fill depth.
Formula used
Rectangular (box)
V = L × W × H
Round (cylinder)
V = π × r² × H, where r = D ÷ 2
Oval (elliptical)
V = π × (a/2) × (b/2) × H
Tapered round (frustum)
V = (πH/3) × (R₁² + R₁R₂ + R₂²)
Tapered rectangular (frustum)
V = (H/3) × (A₁ + A₂ + √(A₁A₂))
A₁ = top area, A₂ = bottom area.
Soil volume scales by effective filled height:
Hsoil = (H × fill%) − drainage.
Conversions: 1,000 cm³ = 1 L. US gallons = L ÷ 3.7854. ft³ = cm³ ÷ 28,316.85.
How to use this calculator
- Measure the planter’s inside length, width, and height.
- Pick the matching shape and select your measurement unit.
- Set fill percentage to keep space for watering or mulch.
- Enter drainage thickness if you add gravel or a drainage mix.
- Optionally add an extra allowance to cover settling.
- Use the results to plan soil bags, raised beds, and weight loads.
- Download CSV for records or PDF for sharing and printing.