Empty pot capacity versus fill around a root ball: quantity checks.
Container capacity is larger than the amount of new mix needed when an existing root ball occupies part of the vessel.
Use the matching calculator
Use this decision sequence
- Write down the common measured requirement before changing an assumption.
- Use selected bag volume or mass, a seed label rate and your supplied planting margins and spacing. No species, mulch depth or sowing rate is chosen.
- Calculate each permitted scenario independently; do not add alternative orders together.
- Carry the chosen product quantities into your material project and use actual supplier prices.
Keep the quantities distinct
| Quantity or assumption | How to use it |
|---|---|
| First basis | Empty pot capacity |
| Second basis | fill around a root ball |
| Decision boundary | Use actual displacement and equivalent loose bag volume. Pot taper, drainage material, compaction and existing mix must be measured rather than silently assumed. |
Worked comparison
Two cylindrical pots 0.4 m in diameter and filled to 0.3 m hold approximately 75.4 L together. Empty-pot capacity would require eight 10 L bags. Subtracting a measured 10 L root ball from each leaves approximately 55.4 L of new mix, or six bags.
Check before using the estimate
Use actual displacement and equivalent loose bag volume. Pot taper, drainage material, compaction and existing mix must be measured rather than silently assumed.
All dimensions, product properties, prices and specifications in this example are illustrative arithmetic inputs. Use the values from your measured plan, selected product data sheet and supplier quote. This guide does not choose construction specifications or certify safety.
Sources and product references
References support the stated product-data distinction. All worked examples are independent illustrative arithmetic.
Calculation and scope checked 2026-10-05. Methods and scope.