Space below ground
Pot volume calculator.
Pot Volume & Repotting Soil Calculator
Look inside the container. Compare usable volumes for straight and tapered pots, then account for material already occupying the new container.
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How to use Pot volume calculator
- Measure inside top and bottom widths or diameters in centimetres. Choose the matching shape.
- Enter usable fill height rather than the outside height or unfilled rim.
- Subtract the volume occupied by an existing rootball or retained material, then enter the nominal bag size.
A worked example
A cylindrical pot with 30 cm inside diameter and 30 cm usable depth holds about 21.21 litres. Tapered pots with the same top diameter and height can hold substantially less.
Assumptions and scope
These are idealised geometric volumes, not root-growth recommendations or load calculations. Drainage layers, irregular walls, packing and settlement change the amount needed. The existing rootball volume is an input, not an estimate made from the plant species.
Results use the entered values and the method described here. Keep units, sampling conditions and the source of the data with your interpretation.