Inputs
Adds extra volume for settling/compaction.
cm
cm
cm
cm
cm
cm
cm
cm
cm
Gap between soil and rim.
cm
Layer of gravel/LECA at bottom.
kg/L
Approximate; varies by recipe and moisture.
Mulch thickness
cm
Top-dress thickness across the exposed surface.
Extra material allowance for mulch only.
Which total to use for bag suggestions.
Examples — L: 5,10,20,25,30,50 • qt: 8,16,32,64 • ft³: 1,1.5,2
Results
Quick Help
- Choose shape and units first.
- Enter inside dimensions, not external.
- Headroom reduces top; drainage subtracts bottom layer volume.
- Mulch displaces mix; plan mulch separately if enabled.
- Reserve adds extra for settling or spillage.
All calculations are approximate; real mixes settle differently.
Downloads
Exports the table and the current calculation summary.
Bulk Totals
Sums combined volumes from the table (and current if checked).
Results & Example Data
Use Add to Results Table to accumulate multiple pots. Preloaded examples included.
| # | Shape | Dimensions (internal) | Headroom | Drainage | Mulch | Reserve % | Total L | Total qt | Total ft³ |
|---|---|---|---|---|---|---|---|---|---|
| Grand Total | 0.00 | 0.0 | 0.000 | ||||||
Formula Used
- Rectangular:
V = L × W × H - Cylindrical:
V = π × (D/2)2 × H - Tapered (frustum):
V = (π × H / 3) × (R2 + Rr + r2), whereRis top radius andris bottom radius.
Headroom adjustment approximates the top gap as a prism/cylinder using top area. Drainage subtracts a bottom layer using base area. Mulch displaces mix using the exposed top area by mulch thickness.
How to Use
- Select the pot shape and measurement units.
- Enter internal dimensions, plus optional headroom and drainage thickness.
- Enable mulch if needed; set thickness and reserve.
- Set a reserve percentage to cover settling or spillage.
- Choose a regional preset, or set bag unit and sizes.
- Click Calculate, then add to the table.
- Check Bulk Totals to plan combined purchases for many pots.
- Use CSV or PDF buttons to export your plan.
FAQs
No. Potting mix settles with moisture and handling. This tool estimates volume based on ideal geometry, headroom, drainage, and mulch, then adds your chosen reserve for safer planning.
Always measure internal dimensions because wall thickness varies between containers. Internal length, width, diameter, and height determine the space available for mix.
Density depends on ingredients and moisture. A common dry estimate for soilless mixes is 0.3–0.5 kg/L. Use your supplier’s data if available for better weight estimates.
Headroom reduces fill height at the top. Drainage subtracts a fixed layer at the bottom. Mulch displaces part of the top fill; use it to plan decorative or water-saving layers.
Yes. Add each calculation to the table. The Bulk Totals panel sums volumes and suggests bags. Use regional presets to match typical bag sizes in your location.