🪴 Potting Soil Calculator
Plan container gardening projects by calculating potting mix volume and bag counts.
Use the depth of soil, not the total pot height.
How to Use This Calculator
Measure containers
Record inside diameter and desired soil depth for each pot size.
Enter quantity
Add more containers or rerun the tool for different pot sizes.
Plan mix purchase
Compare bag counts against bulk or homemade mix options before planting.
Formula
Volume per pot (cu in) = π × (Diameter ÷ 2)2 × Height
Total Volume (cu ft) = Volume × Count ÷ 1728
Bag Count = Total Volume ÷ Bag Size
Adjust for containers with tapered sides by using average diameter or using nursery trade container volumes.
Full Description
Container gardens require lightweight, well-draining mixes. Estimating volume ahead of time simplifies bulk purchases and prevents mid-project shortages.
Consider blending compost, perlite, and peat or coco coir to customize texture and drainage for specific plant needs.
Frequently Asked Questions
How do I calculate for rectangular planters?
Multiply length × width × soil depth, then convert cubic inches to cubic feet and add to the total.
Should I fill pots to the brim?
Leave 1–2 inches of headspace for watering to prevent overflow.
Can I reuse potting mix?
Refresh with compost and perlite; sterilize if disease was present.
Why is my mix settling?
Water the mix after filling. Settling is normal; top off before planting if needed.