Potting Soil Calculator
Choose a rectangular planter or a round pot, enter its dimensions and how many you have, and get the total potting soil volume needed. Real fill volume can vary with root balls, drainage layers, and settling.
Last updated: September 25, 2026
Frequently asked questions
Should I fill the container all the way to the rim?
Usually not. Most growers leave an inch or two of headspace below the rim for watering, so measure your intended fill depth rather than the container's full height.
How is this different from the Compost or Mulch Calculators?
Those are sized for outdoor beds and yards, using depth over a garden area. This tool is built around container geometry - rectangular planters or round pots - and a number of containers, which is a different shape problem.
Why does the actual soil used differ from the calculated volume?
A root ball or plant already growing in the container takes up space, some growers add a drainage layer of gravel or broken pot pieces at the bottom, and soil settles and compacts after watering, all of which reduce how much fresh soil you actually add.
Can I calculate several identical pots at once?
Yes. Enter the dimensions for one container and the number of containers, and the tool multiplies the volume for you.
Why do I need to enter my own bag size?
Bagged potting soil is sold in different volumes by different brands and regions, so there is no single correct bag size to assume. Enter the volume printed on your product's bag.
Does this account for soil that compacts after watering?
No, it calculates geometric volume only. Buying a bit extra is a reasonable practice since soil volume typically decreases somewhat after the first thorough watering.