A little maths.
A lot less guessing.
Two free tools to help with the practical details. Your inputs stay in this page.
Container volume calculator
The filled-in dimensions are an example. Replace them with inside measurements up to your intended fill level.
For the example pot
17.7 litres4.67 US gallons per potCalculate again after changing dimensions.
How the estimate works
Cylinder: π × radius² × height. Box: length × width × height. Tapered round pot: π × height × (top radius² + top radius × bottom radius + bottom radius²) ÷ 3. One litre = 1,000 cm³; one US gallon = 3.785411784 litres.
This is an empty geometric volume estimate. Roots, irregular shapes, settling and unfilled space change how much growing mix you actually need.
Seed-starting date planner
Use a locally suitable outdoor planting date and the “weeks before planting” range from your seed packet. This tool does not predict frost dates.
Enter the week range from your seed packet. No timing is assumed for your crop.
Your sowing window
Start with your local dateAdd your seed packet’s timing, then calculate.
A date calculation is not a planting recommendation. Check forecast conditions before moving plants outdoors.
Read the seed-starting guide