That's an excellent question! Knowing the right amount of soil is key for healthy plants and efficient gardening. For our standard medium-sized planter box, which measures approximately 24 inches in length, 12 inches in width, and 12 inches in height, you can easily calculate the soil volume needed.
Here’s the simple math: Multiply the Length x Width x Height. Using our example: 24” x 12” x 12” = 3,456 cubic inches. To convert this into a more standard gardening measurement, divide cubic inches by 1,728 to get cubic feet. So, 3,456 / 1,728 = 2 cubic feet of soil.
Therefore, to fill one of our medium planter boxes, you will need 2 cubic feet of potting soil. Most bags of potting mix are sold in quantities like 1 cubic foot or 2 cubic foot bags. This means you would typically need one 2-cubic-foot bag or two 1-cubic-foot bags.
A helpful pro tip: We recommend leaving about 1-2 inches of space between the soil surface and the top rim of the planter box. This "headspace" allows for efficient watering without overflow. You might factor this slight reduction into your purchase, or simply use the full 2 cubic feet and top up slightly as the soil settles after the first few waterings. Always choose a high-quality potting mix designed for containers to ensure proper drainage and aeration for your plants' roots.