Potting Soil Calculator
Find how much potting mix you need to fill round, tapered or box pots and planters, in quarts, liters and cubic feet.
Potting mix needed
19.6 quarts
- Liters
- 18.5 L
- Cubic feet
- 0.65 ft³
1 pots filled 100% need about 19.6 quarts of potting mix, which is about 18.5 liters.
Calculation breakdown
| Step | Formula | Result |
|---|---|---|
| Volume of one pot (cubic inches or cubic centimeters) | π × (12 ÷ 2)² × 10 | 1,131 |
| Total potting mix | 1 pots × 100% full | 19.6 qt |
How it works
Choose the pot shape, enter its inside size, the number of pots and how full to fill them.
Worked example
Three round pots, each 12 in across with 10 in of soil, filled to 90%:
- One pot: π × 6² × 10 = 1,130.97 cubic inches
- At 90% full: 1,130.97 × 0.9 = 1,017.9 cubic inches
- Three pots: 3,053.6 cubic inches ÷ 57.75 = 52.9 quarts, which is about 50 liters
Rounding
Volumes are shown to one decimal place. Calculations use the unrounded values.
Sources
Frequently asked questions
How much potting soil do I need for a pot?
Work out the volume of the pot and fill it to the level you want. A round pot 12 inches across and 10 inches deep holds π × 6² × 10 = 1,131 cubic inches, which is about 19.6 quarts. The calculator does this for round, tapered and box pots.
How do I find the volume of a tapered pot?
A pot that is wider at the top than the bottom is a cone frustum. Its volume is π times the height over 3 times the sum of the squared top radius, the top radius times the bottom radius, and the squared bottom radius. Enter the top and bottom diameters and the calculator applies it.
How many quarts are in a cubic foot?
A US quart is 57.75 cubic inches, a quarter of a gallon. A cubic foot is 1,728 cubic inches, so it holds about 29.92 quarts. Bags of potting mix are usually labelled in quarts or cubic feet, so the calculator shows both.
Should I fill the pot to the rim?
Usually you leave some room below the rim for watering. Enter how full you plan to fill the pot in the advanced options, for example 90%, and the calculator reduces the volume to match.
How do I measure the soil depth?
Measure from the bottom of the pot, inside, up to the level of the soil you want. For a pot with a drainage layer, subtract the depth of that layer. Use inside measurements, since pot walls take up space.
Estimates only. Loose potting mix settles after watering, so buy a little extra.