Mulch volume calculator

Enter the dimensions of the bed you're mulching. Get cubic yards, cubic feet, and the number of 2 cubic-foot bags you need — defaulted to the 2-3 inch depth recommended by Cornell Cooperative Extension for woody-plant beds.

Bed dimensions

You need approximately

8 bags

Per Cornell Cooperative Extension, 2-3 inches of mulch over a bed's root zone is the recommended depth. Less than 2 inches doesn't suppress weeds reliably. More than 4 inches can promote crown rot on perennials and trap moisture against tree trunks. Keep mulch a 2-inch ring away from any plant stem or trunk.

Mulch depth guide

2 inches: appropriate over perennial beds and around herbaceous plants where the crowns are at ground level. Suppresses most weeds, holds moisture, doesn't risk crown rot.

3 inches: the standard for shrub borders, foundation plantings, and around small trees. Cornell Extension's baseline recommendation for woody plants. Top up annually as the mulch decomposes into the soil.

4+ inches: reserved for paths or unplanted areas where weed suppression is the only goal. Avoid this depth over root zones — it can trap moisture against bark and promote rot.

Volcano mulching is wrong. Mounding mulch up against tree trunks (you've seen the cone-shape in commercial landscapes) causes bark rot, harbors voles, and weakens the tree. Mulch should always have a 2-inch ring of bare soil around the trunk — the "donut" method, not the "volcano."

Sources: Cornell Cooperative Extension, Penn State Extension, Missouri Botanical Garden.