Potting Soil Calculator — Potting Mix for Containers
Choose your container shape and enter its dimensions to calculate how much potting mix you need. Results are in gallons, liters, and cubic feet. The volume is the full container capacity — fill to your desired level.
What this calculator determines
It calculates the potting mix volume needed to fill a container to a chosen depth, for round, rectangular, or square planters.
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Examples
12 in round pot, 10 in fill
12 in diameter, 10 in deep
Calculation
- Radius: 6 in
- Volume: π × 6² × 10 = 1,131 cu in
- Gallons: 1,131 × 0.004329 = 4.89 gal
4.89 gal (18.5 L)
Assumptions & Conventions
- Shape approximation
- Round pots are modeled as a cylinder (π × (diameter/2)² × depth); rectangular and square planters as a box. Real pots may taper.
- Fill depth
- Enter the depth you actually want to fill, not the full container height — leave headroom for watering.
- Unit conversions
- 1 cubic inch = 0.004329 gallons; 1 gallon = 3.785 liters.