Buying soil often begins with a measurement of volume, typically the cubic foot, which can be difficult to visualize. This unit represents the three-dimensional space an object occupies, but its connection to practical garden material is not intuitive. Understanding how much soil is contained within two cubic feet (2 cu ft) allows for greater accuracy in purchasing and planning garden projects. This article provides context for visualizing and applying this common unit of volume.
Visualizing Two Cubic Feet
A cubic foot is defined as the volume of a cube measuring one foot long, one foot wide, and one foot high, symbolized as \(\text{cu ft}\). Two cubic feet represent a volume twice that size, which can be configured in various shapes. For example, two cubic feet of soil could fit into a container measuring one foot high, one foot wide, and two feet long.
For comparison, this volume is roughly equivalent to a large storage tote or could fill just over 15 gallons of liquid volume. Another way to imagine this volume is by considering a pair of standard five-gallon buckets filled to the brim. A single bag of two cubic feet of soil is slightly larger than a typical microwave oven.
Calculating Coverage Area
The transition from a confined volume to a spread-out area requires a calculation that incorporates depth. The fundamental relationship is that Volume equals Area multiplied by Depth, or \(V = A \times D\). To determine the square footage of coverage, the fixed volume of two cubic feet must be divided by the desired depth, with all units converted to feet.
For instance, covering a planting bed with a thin layer of soil, such as two inches deep, requires converting that depth to feet (2/12 = 0.167 feet). When two cubic feet is divided by 0.167 feet, the result is a coverage area of about 12 square feet. This is enough to cover a space roughly 3 feet by 4 feet.
If a deeper layer of four inches is needed for top-dressing or filling a flower border, the coverage area decreases significantly. Four inches converts to 0.333 feet, meaning two cubic feet of soil will cover approximately six square feet. This depth is recommended for established garden beds to suppress weeds and maintain moisture levels. For very shallow applications, such as a half-inch layer for overseeding a lawn, the two cubic feet can cover up to 48 square feet.
Comparing Cubic Feet to Purchasing Units
Soil is commonly sold in bags labeled by volume, such as \(1.5 \text{ cu ft}\) or \(2 \text{ cu ft}\). This volume measurement is distinct from soil purchased in bulk, which is typically sold by the cubic yard, equivalent to 27 cubic feet. Understanding the difference is important for large projects, as two cubic feet is a small fraction of a cubic yard.
A significant factor in handling bagged soil is its weight, which varies based on the type of soil and its moisture content. Dry, loose potting mixes, which often contain lighter materials like peat moss, will weigh less than dense topsoil or loam. A two-cubic-foot bag of garden soil can weigh approximately 80 to 120 pounds, depending on how much water it holds.
Soil density can range from about 74 to 110 pounds per cubic foot, meaning two cubic feet of soil will almost always exceed 140 pounds in its wet state. Because a single bag can be quite heavy to lift and move, having a cart or wheelbarrow available for transport is recommended.