Thank you for your question about soil quantity for our large urban planter boxes! This is one of the most common and important questions we receive, as getting the soil volume right is crucial for your plants' health and the planter's proper function.
Our standard large urban planter box measures 36 inches in length, 12 inches in width, and 12 inches in height. To calculate the soil volume needed, simply multiply these dimensions together. Here's the calculation:
36" (L) × 12" (W) × 12" (H) = 5,184 cubic inches
To convert this to cubic feet (the standard measurement for soil bags), divide by 1,728 (since there are 1,728 cubic inches in one cubic foot):
5,184 ÷ 1,728 = 3 cubic feet
Therefore, you will need exactly 3 cubic feet of soil to fill one of our large urban planter boxes to the brim. We recommend filling to about 1-2 inches below the top edge to allow for watering space and prevent soil washout.
Most bagged potting soil is sold in measurements of cubic feet, so you would need three 1-cubic-foot bags, one 3-cubic-foot bag, or equivalent combinations to fill your planter box perfectly. Remember that soil settles over time, so you may want to have a small amount extra for top-ups after the initial watering and settling period.
For optimal plant health, we recommend using a high-quality potting mix specifically formulated for container gardening, as these provide better drainage and aeration than regular garden soil. Happy planting!