The basic mulch volume formula
Mulch quantity starts with bed area. For a rectangular garden bed, multiply length × width to get square feet. Then multiply by depth in feet to get cubic feet. Divide by 27 to convert to cubic yards — the unit bulk mulch is sold in.
Example: a 12 ft × 8 ft bed at 3 inches deep. Area = 96 sq ft. Depth in feet = 3 ÷ 12 = 0.25 ft. Volume = 96 × 0.25 = 24 cu ft. Cubic yards = 24 ÷ 27 ≈ 0.89 cu yd. Round up to 1 cubic yard when ordering bulk.
Irregular beds can be split into rectangles or measured as an average width along a curved border. For tree rings, use π × radius² for area, then apply the same depth math.
Measuring multiple beds in one project
Most landscaping jobs include several beds — foundation plantings, island beds, tree rings, and side yards. Calculate each bed separately, then add cubic yards for a single delivery or truckload.
A typical suburban front yard might include: 40 sq ft foundation bed + 120 sq ft island bed + three 25 sq ft tree rings. At 3 inches depth, that totals roughly 2.2 cubic yards before waste.
- Foundation beds: measure along the house, include corners
- Island beds: length × width at the widest points
- Tree rings: outer diameter minus inner (no-mulch) zone
- Paths with mulch: treat like a narrow rectangle
Adding waste and settling allowance
Add 10% extra for uneven ground, spillage, and settling over the first season. Beds with steep edges or lots of curves may need 15%. Our calculator includes an adjustable waste percentage.
Fresh mulch fluffs higher than aged mulch — a truck that looks “full” at delivery will settle after rain and foot traffic. Ordering slightly more avoids a second trip for half a yard.
Using the calculator for your yard
Enter up to five beds with feet-and-inch dimensions. Set depth (default 3 inches), material type, and waste %. You get cubic yards, standard 2 cu ft bag counts, and a copyable shopping list.
Use our mulch calculator for instant totals, or read our cubic yards guide if you prefer pencil-and-paper math.