How the calculator works
Mulch coverage is pure volume: cubic yards = area × (depth ÷ 12) ÷ 27. The classic shortcut is that one cubic yard covers 108 sq ft at 3″ deep, or 162 sq ft at 2″.
Worked example: 300 sq ft of beds at 3″ deep is 300 × 0.25 = 75 cu ft = 2.8 cubic yards, or 38 two-cubic-foot bags.
How deep should mulch be?
- 3 inches is the sweet spot for weed suppression and moisture retention with wood mulches.
- 2 inches for an annual refresh over existing mulch, or for fine mulches that mat down.
- Never more than 4 inches. Deeper starves roots of oxygen, and mulch piled against trunks ("mulch volcanoes") rots bark and invites disease. Keep a 3″ gap around stems and trunks.
Bags vs bulk
Bagged mulch costs roughly two to three times more per cubic foot than bulk, but it's cleaner to transport and lets you spread the job over weekends. The practical crossover: below about 2 yards, bags are fine; above 3–4 yards, bulk delivery pays for itself even with the delivery fee. A standard pickup bed holds about 2 loose cubic yards of mulch, heaped.
Coverage quick-reference (per cubic yard)
- 1″ deep → 324 sq ft
- 2″ deep → 162 sq ft
- 3″ deep → 108 sq ft
- 4″ deep → 81 sq ft