How to use this calculator
- Measure the bed. Length and width of the planting bed in feet. For irregular shapes, break the bed into rectangles and add the results.
- Pick a depth. 2 inches around annuals, 3 inches around shrubs, 4 inches around trees. Less than 2 inches will not suppress weeds; more than 4 chokes the roots.
- Read your result. You get cubic yards (bulk delivery), cubic feet, and bag counts. A yard at 3 in depth covers about 108 sq ft.
- Plan delivery vs bags. Bulk mulch is roughly half the price per yard of bagged mulch. Above 3 yards, delivery almost always wins.
Formula
Coverage (ft²) = (Cubic yards × 27) ÷ Depth in feet
Worked example
A 20 ft × 8 ft mulch bed at 3 inches deep needs 160 × 0.25 = 40 ft³ ÷ 27 = 1.5 cubic yards. That is about 20 bags of 2 cu ft mulch, or one bulk delivery.
Tips for accurate results
- A cubic yard of mulch covers 108 sq ft at 3 inches deep — the most common landscape depth.
- Refresh by ½ to 1 inch each spring; do not pile new on top of compacted old mulch (creates a moisture barrier).
- Keep mulch 2–3 inches away from tree trunks and stems to prevent rot and pest damage.
- Bulk mulch is sold by the cubic yard. 1 yd³ ≈ 13–14 retail bags of 2 cu ft.