From Bed Dimensions to Cubic Yards

Mulch is sold by volume, so every order begins with the same arithmetic: area times depth, converted into cubic yards by dividing by 27. The step most people skip is that depth belongs in feet, not inches, and a three-inch layer is only a quarter of a foot. A twenty by ten foot bed at three inches is fifty cubic feet, which sounds substantial until it converts to just 1.85 cubic yards. Suppliers quote in yards, garden centers sell in two and three cubic foot bags, and reconciling those two units is where most ordering mistakes start.

Why Depth Matters More Than Coverage Claims

A cubic yard covers 324 square feet at one inch, 162 at two inches, and 108 at three. Those numbers are fixed geometry, yet bagged products often advertise coverage without stating the depth assumed, which makes bags look far more productive than they are. Two to three inches is the working range for established beds: enough to keep light off weed seeds and slow evaporation, not so much that oxygen exchange at the root zone suffers. Vegetable beds do well at two inches, tree rings and perennial borders at three to four.

Settlement Is Not the Same as Waste

Waste covers what you lose during installation — spillage, uneven spreading, material that drifts past the bed edge. Settlement is what happens afterward. Organic mulch compacts under rain and foot traffic while soil organisms consume it from below, and the two effects together take shredded hardwood down to roughly 85% of its installed depth within a season. Compost fares worse at around 70% because decomposition is the entire point of the material. Rubber mulch barely moves. This calculator applies waste to the order and reports settled depth separately, so the top-up volume next spring is a planned figure rather than a surprise.

Deciding Between Bags and Bulk

Bagged mulch at five dollars for two cubic feet works out to about $67 per cubic yard, against $25 to $50 for bulk plus a flat delivery fee that typically runs $50 to $80. The crossover generally lands between two and three yards, but the honest comparison depends on your own delivery quote and bag price, which is why both appear as editable inputs. Bags still win when a truck cannot reach the site, when material must be carried through a gate, or when the job will be spread across several weekends and a pile in the driveway is not practical.