The Mathematics of Landscaping

One of the most difficult parts of landscaping is visualizing exactly how much material you need. Unlike water, mulch and dirt do not level themselves perfectly, and it is incredibly easy to vastly underestimate the volume required to fill a garden bed.

To accurately calculate mulch, you must convert three-dimensional space into the universal landscaping unit: the Cubic Yard.

What is a Cubic Yard?

A cubic yard is a volumetric measurement representing a block of space that is exactly 3 feet long, 3 feet wide, and 3 feet tall. Because 3 × 3 × 3 = 27, there are exactly 27 cubic feet in one cubic yard.

When you call a bulk landscape supplier, they will only sell dirt, mulch, and rock by the cubic yard. A standard pickup truck bed can physically hold about 1.5 to 2.0 cubic yards of material before it starts spilling over the sides.

Why Depth Matters

The depth of your mulch layer completely dictates its functionality.

• 1 Inch (Cosmetic Only): Spreading mulch 1 inch thick looks nice for a week, but it will do absolutely nothing to suppress weeds. Sunlight will easily penetrate the thin layer of wood chips, and weeds will immediately grow through it.
• 3 Inches (Industry Standard): This is the golden rule of landscaping. A 3-inch layer is thick enough to completely block sunlight from reaching the soil, killing off dormant weed seeds. It is also thick enough to insulate the soil, trapping moisture during the scorching heat of summer so you don't have to water your plants as frequently.
• Over 4 Inches (Dangerous): Adding too much mulch restricts oxygen flow to the soil and traps too much water. If you pile heavy, wet mulch directly against the bark of a tree, it will cause the bark to rot and introduce fungal diseases that can kill the plant.