Figuring out how much soil you need for your urban planter boxes is a common gardening hurdle. Buying too much is wasteful, and too little means a last-minute trip to the store. The process is straightforward: you calculate the volume of each box and then multiply by three. Here is a simple, step-by-step method to get the right amount.
First, you need to measure your planter boxes. Grab a tape measure and record the internal length, width, and height in feet. For example, a common box might be 2 feet long, 1 foot wide, and 1 foot high.
Next, calculate the volume of a single box using the formula for a rectangular prism: Length x Width x Height. Using our example: 2 ft x 1 ft x 1 ft = 2 cubic feet. This is the volume of one planter box.
Since you have three boxes, multiply the single box volume by three. In our example: 2 cubic feet x 3 = 6 cubic feet of soil in total.
Most bagged soil is sold in quarts or cubic feet. There are 25.75 dry quarts in one cubic foot. Therefore, for 6 cubic feet, you would need 6 x 25.75 = 154.5 dry quarts. It's always wise to buy a little extra—about 10%—to account for settling. In this case, consider getting around 170 dry quarts.
For different box sizes, simply plug your measurements into the same formula. If your measurements are in inches, first divide each number by 12 to convert to feet, then calculate the volume. Remember to use the internal dimensions for accuracy, as the soil fills the inside space, not the thicker outer walls.
By following this method, you can confidently purchase the perfect amount of soil to get your urban garden thriving without any guesswork or waste. Happy planting