Terrarium Substrate Volume Calculator
A closed terrarium stacks a drainage layer, a charcoal layer (for filtering), then soil. Treating the container as a cylinder, the base area (radius squared times π) times the combined layer depth gives the volume, converted from cm³ to liters by dividing by 1000.
Your numbers
Substrate volume needed
3.14L
Total layer depth
10cm
Formula
Substrate volume needed = π × (Container diameter (cm) ÷ 2)² × (Drainage layer depth (cm) + Charcoal layer depth (cm) + Soil layer depth (cm)) ÷ 1000
Keep the soil layer thicker than the drainage layer so roots have room to grow. Don't skimp on drainage depth — standing water rots roots.
What to enter
| Input | Default | Accepted range |
|---|---|---|
| Container diameter (cm) (cm) | 20 | 5 ~ 80 |
| Drainage layer depth (cm) (cm) | 3 | 1 ~ 10 |
| Charcoal layer depth (cm) (cm) | 1 | 0 ~ 5 |
| Soil layer depth (cm) (cm) | 6 | 2 ~ 20 |
Step by step
Quick reference table
Results when only Container diameter (cm) (cm) changes and everything else stays put.
| Container diameter (cm) (cm) | Substrate volume needed (L) | Total layer depth (cm) |
|---|---|---|
| 10 | 0.79 | 10 |
| 15 | 1.77 | 10 |
| 20 | 3.14 | 10 |
| 30 | 7.07 | 10 |
| 40 | 12.57 | 10 |
What each result means
| Result | At default values |
|---|---|
| Substrate volume needed (L) | 3.14 |
| Total layer depth (cm) | 10 |
Common mistakes
Keep the soil layer thicker than the drainage layer so roots have room to grow. Don't skimp on drainage depth — standing water rots roots.
Frequently asked questions
QHow is Terrarium Substrate Volume Calculator calculated?
Substrate volume needed = π × (Container diameter (cm) ÷ 2)² × (Drainage layer depth (cm) + Charcoal layer depth (cm) + Soil layer depth (cm)) ÷ 1000 — A closed terrarium stacks a drainage layer, a charcoal layer (for filtering), then soil. Treating the container as a cylinder, the base area (radius squared times π) times the combined layer depth gives the volume, converted from cm³ to liters by dividing by 1000.
QCan you walk through an example?
With Container diameter (cm) 20cm, Drainage layer depth (cm) 3cm, Charcoal layer depth (cm) 1cm, Soil layer depth (cm) 6cm, the answer is Substrate volume needed 3.14L.
QWhat do I need to enter?
Enter Container diameter (cm), Drainage layer depth (cm), Charcoal layer depth (cm), Soil layer depth (cm). The result recalculates as you type, and an empty box counts as zero.
QHow much does the answer move if I change a number?
Changing only Container diameter (cm) (cm) moves the answer to Container diameter (cm) (cm) 10 → Substrate volume needed (L) 0.79 and Container diameter (cm) (cm) 40 → Substrate volume needed (L) 12.57. The table below lays out five steps.
QHow are the numbers rounded?
Money is shown to the nearest whole unit, percentages to one decimal place and everything else to two. What you see is rounded; the calculation itself carries the unrounded value forward.
QAnything to watch out for?
Keep the soil layer thicker than the drainage layer so roots have room to grow. Don't skimp on drainage depth — standing water rots roots.
Related calculators
Materials differ in density and absorption. If your label states a figure, use it — the defaults here are only common values.