How Much Mulch Do I Need?
Convert bed area and depth to cubic yards or bags, and decide how deep to spread mulch.
Area × depth
Multiply each bed’s length by width, add them up, then multiply by depth in feet. A 3 in layer is 0.25 ft. A 10 × 10 ft bed at 3 in needs 25 cubic feet — just under one cubic yard.
Bags versus bulk
Bagged mulch usually comes in 2 or 3 cubic foot bags, so one cubic yard equals 13.5 two-foot bags or 9 three-foot bags. For more than a yard or two, bulk delivery is typically cheaper.
How deep?
Two to three inches suppresses weeds without smothering roots. Keep mulch a few inches away from tree trunks and plant stems to avoid rot.