Potting soil calculator
Calculate how many quarts of potting soil fit in a round or square pot or a planter box, and how many bags to buy to fill several pots, subtracting the drainage layer.
How to useHow much soil does the pot need?
Available in: 
Potting soil calculator: what it is for
Enter the measurements of the top, the bottom and the height of the pot, the drainage layer and how many pots you will fill. The calculator accounts for pots that taper toward the bottom and shows the quarts of soil, the drainage and the number of bags you need.
How to use
- Choose the shape of the pot.
- Type the measurements and the drainage.
- See the quarts and the bags of soil.
When to use it
- Repotting plants into bigger pots.
- Filling planter boxes on the balcony or patio.
- Buying potting mix without waste.
Frequently asked questions
How do I calculate the volume of a round pot?
Pots that taper toward the bottom are a truncated cone: volume = π × height × (R² + R × r + r²) ÷ 3, where R and r are the radii of the top and the bottom. The tool does the math with the measurements in inches and shows the result in quarts and cubic feet.
Do I need a drainage layer?
For most plants, a 1 to 2 inch layer of clay pebbles or gravel at the bottom, covered with landscape fabric, keeps the roots from getting waterlogged. It is subtracted from the soil volume.
Bags in quarts or cubic feet?
Potting mix is sold by volume: small bags in quarts (8, 16 or 32 qt) and larger ones in cubic feet. 1 cubic foot is about 25.7 quarts, so a 2 cu ft bag holds about 51 quarts.
Is it really free?
Yes, 100% free. No sign-up, no subscription and no usage limits. All Tools123 tools are free and run right in your browser.