Potting Soil Calculator

A potting soil estimate helps gardeners buy enough growing medium without carrying home a large surplus. Containers are three-dimensional, so surface length and width alone are not enough; the intended fill depth also matters. This calculator handles rectangular planters and raised beds as box-shaped volumes, and round pots as cylinders. It reports total liters, equivalent cubic feet, and the number of whole bags needed for all identical containers. For a rectangular container, inside length is multiplied by inside width and soil depth. Measurements in centimeters produce cubic centimeters, and one thousand cubic centimeters equal one liter. For a round container, the calculator uses the circular area based on half the diameter, then multiplies by depth. The volume of one container is multiplied by the entered quantity. Liters are converted to cubic feet using 28.316846592 liters per cubic foot. Bag count is always rounded up because a partial final bag still has to be purchased. Measure internal dimensions rather than the outside of a thick-walled pot or raised-bed frame. Soil depth may be less than container height when space is reserved below the rim for watering. Existing root balls, drainage layers, permanent reservoirs, stones, logs, or other inserts displace some mix. Conversely, fresh potting media can settle after watering and over time. For these reasons, the geometric result is a baseline. A modest reserve is often useful for settling, topping up, spills, and future maintenance, but the appropriate allowance depends on the material and project. Use a growing medium suited to the plants and container. Garden topsoil alone may drain poorly and compact in pots, while raised beds can use blends designed for larger volumes. Check product labels because bag sizes and measured volumes differ across markets, and compressed products may expand after hydration. When several planters have different dimensions, calculate each group separately and add the liters before deciding how many bags to buy. Irregular tapered pots are not perfect cylinders; measuring a representative average diameter gives a closer approximation. This calculator estimates volume only and does not determine mix composition, fertilizer, bulk weight, structural loading, or drainage requirements.