Measure inside the container
For a rectangular planter, volume in litres is length × width × fill depth in centimetres ÷ 1,000. For a straight-sided round pot, use π × radius² × fill depth ÷ 1,000. One inch equals 2.54 cm.
Plan the purchase
We multiply by the number of containers, add your chosen allowance, then round up to full bags. The extra allowance is your choice; it is not a guaranteed settling rate.
Know the limits
The round option assumes a cylinder, not a tapered flowerpot. Root balls and other contents reduce the volume available for new mix. This tool does not calculate weight or confirm whether a balcony can support a planter.