Potting Soil Calculator
Choose your container shape and enter its dimensions to calculate how much potting soil you’ll need to fill it.
What this calculator does
The Potting Soil Calculator estimates the volume of soil needed to fill a round pot or a rectangular planter, given in quarts, cubic feet, and liters — the common units potting mix is sold in.
How the formula works
For round pots, volume uses the cylinder formula V = π × r² × height. For rectangular planters, it uses V = length × width × height. The result in cubic inches is then converted to cubic feet (÷1,728), quarts (÷57.75), and liters (×0.0163871) to match common bag labeling.
- Bagged potting mix is most often sold by the quart, 8-quart, or cubic-foot bag
- Leave the fields for the shape you’re not using at any value — only the selected shape’s fields are used
A note on accuracy
Actual soil needed may be slightly less than calculated volume once compacted mix settles, and pots with drainage material or false bottoms will need somewhat less soil than the full container volume.