Figure out how much potting soil to buy for your containers, whether round pots or rectangular planter boxes.
Container Soil Calculator
Enter your pot's shape and dimensions to estimate potting soil volume and how many bags to buy.
How this is calculated: Volume is computed from your pot's geometry (cylinder for round, box for rectangular), filled to 90% of height to leave room for watering, then converted using the standard dry-quart conversion (1 cubic foot = 25.7 dry quarts). Note that dry quarts differ from liquid quarts – bagged soil is always sold in dry quarts, which is what this calculator uses.
Potting soil is sold by dry quarts or cubic feet, and one cubic foot equals about 25.7 dry quarts – a different measurement than the liquid quarts used for cooking, which trips up more shoppers than you’d expect. This calculator handles that conversion for you.
Filling to 90% of your container’s height leaves room for watering without soil spilling over the rim, which is standard practice for most potted plants and raised containers.
If you’re planting several matching pots at once, entering the pot count here saves you from multiplying a single-pot estimate by hand and rounding separately for each one.
Where These Numbers Come From
The 25.7 dry-quart-per-cubic-foot conversion is a standard, widely-published figure for soil, compost, and mulch. Bag sizes listed reflect common sizes sold at most garden centers; check your specific product’s label since some brands round bag sizes slightly differently.