What is the Potting Soil Calculator?
The Potting Soil Calculator estimates how much soil you need to fill your pots, planters or grow boxes. Enter the dimensions of a single container, pick its shape, and multiply by how many containers you are filling. The tool reports the total volume in liters, cubic feet and US dry quarts so you can match it to bagged soil sizes sold in any unit.
How to use it
Choose Round / Cylindrical and enter the pot diameter and height, or choose Rectangular and enter length, width and depth — all in centimeters. Set the number of containers and read off the total. The "Volume per container" row shows how much one pot holds.
The formula explained
For a round pot the soil volume is the volume of a cylinder, $$V = \pi r^2 h$$ where \(r\) is half the diameter. For a rectangular planter it is simply $$V = L \times W \times H$$ The result in cubic centimeters is divided by 1,000 to get liters (1 liter = 1,000 cm³), by 28,316.85 for cubic feet, and by 1.1012 to get US dry quarts.
Worked example
A round pot 25 cm in diameter and 20 cm tall has \(r = 12.5\) cm, so $$V = \pi \times 12.5^2 \times 20 \approx 9{,}817 \text{ cm}^3 \approx 9.82 \text{ liters per pot}$$ Five such pots need about 49.1 liters of soil, or roughly 1.73 cubic feet.
FAQ
Should I fill the pot to the brim? No — leave 2–3 cm of headroom for watering, so you may need slightly less than the calculated volume.
How do bag sizes compare? Soil is often sold in liters or cubic feet; 1 cubic foot ≈ 28.3 liters. Use the cubic feet figure to match US bags.
Does soil settle? Yes, potting mix compacts after watering, so buy a little extra to top up.
