Mulch Calculator
Cubic yards and bags of mulch needed for your bed from its length, width and depth.
How it works
cubic feet = length × width × depth(in) ÷ 12 · cubic yards = cubic feet ÷ 27
Depth in inches is divided by 12 to get feet, then multiplied by the bed’s footprint for cubic feet. Suppliers sell by the cubic yard (27 cubic feet), while stores sell 2-cubic-foot bags, so both figures are shown. Bags are rounded up — a part-bag still has to be bought.
Worked example
A 12 × 4 ft bed mulched 3 inches deep: 12 × 4 × 0.25 = 12 cubic feet. That’s 12 ÷ 27 = 0.44 cubic yards, or 6 two-cubic-foot bags.
Frequently asked questions
How deep should mulch be?
2–3 inches is the standard for beds — enough to hold moisture and suppress weeds without smothering roots. Keep it a few inches back from trunks and stems; "mulch volcanoes" rot bark.
How much does a cubic yard weigh?
Dry wood mulch runs 400–600 lb per yard; fresh or wet loads can approach 800–1,000 lb. One yard fills a typical pickup bed level full.
How often does mulch need topping up?
Organic mulch breaks down — plan on refreshing about an inch a year. Measure remaining depth and enter just the difference here.
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This calculator is for educational purposes. Double-check important results before acting on them.