Figuring out how much soil to buy for your 24-inch urban planter is a simple calculation that ensures you get just the right amount. First, you need the interior dimensions. For a typical rectangular box that is 24 inches long, let's assume it's 8 inches wide and 8 inches deep. The formula for volume is Length x Width x Depth.
So, 24 inches (L) x 8 inches (W) x 8 inches (D) = 1,536 cubic inches. To convert this to cubic feet—the standard unit for bagged soil—divide by 1,728 (the number of cubic inches in a cubic foot). 1,536 ÷ 1,728 = approximately 0.89 cubic feet.
Therefore, you will need just under 1 cubic foot of potting mix to fill your planter box. Most bagged soil is sold in quantities like 1 cubic foot, 1.5 cubic feet, or 2 cubic feet. Purchasing a 1-cubic-foot bag should be perfect, with a little left over for settling. Remember, always use a high-quality potting mix designed for containers, not regular garden soil, to ensure proper drainage and aeration for your plants' roots.