Landscape rock, sometimes known as decorative rock, can make a delightful addition to garden, lawn, or landscape. It adds diversity of texture and color, along with a sense of gravity, to plantings such as flowers, trees, shrubs, and grass. Landscape rock can be used to frame landscape design elements, or to create borders, or walkways. Landscape rock is especially well-suited to setting off ponds, pools, and waterfalls. Decorative rock is available in a variety of colors, types, and sizes. Figuring out how much rock you will need to fill a given space is a matter of formula.
Measure the width of the area. Use the tape measure to determine how wide the area is, in feet.
Measure the length of the area. Determine the length, in feet, of the area where you plan to install the decorative rock.
Multiply the width by the length. Total area equals width times length. For example, if the width of the area is 3 feet and the length is 4 feet, the total area is 12 square feet.
Figure out the depth of your layer of rock. Your retailer or contractor should be able to help you with this. The depth you need can depend on how dry or muddy the area you want to fill may be. A muddy space will require a thicker layer of rock than a dry one.
Convert the depth measurement from inches to feet. To accomplish this, divide the number of inches by 12. If, for example, you want a depth of 6 inches of rock, divide 6 by 12 to get 0.5 feet. Six inches equals 1/2 foot.
Calculate cubic feet of the area. The formula for cubic feet is length times width times depth. In our example, the calculation would be four times three times 1/2. That computes to 6 cubic feet.
Purchase enough landscape rock to cover the area. If the area to be covered is 6 cubic feet, for example, and each bag of rock covers 2 cubic feet, you will need three bags of landscape rock to fill the space. Consult with your landscape rock retailer to be sure of buying enough rock to cover the area.