How much mulch you need
Mulch volume is cubic yards = area × depth in inches ÷ 324. A 500 sq ft bed at 3 inches deep is about 4.63 cubic yards. The 324 constant comes from 12 inches × 27 cubic feet per yard. Bed areas are easiest to total with the square footage calculator.
How to use this calculator
Enter the bed area in square feet and the depth in inches. The result shows cubic yards plus an estimate in 2-cu-ft bags. Spreading a slab instead? The volume math matches the concrete calculator. Bulk suppliers quote by the yard, which the square feet to cubic yards calculator converts.
Depth guidance
Use 2–3 inches for most beds and 3–4 inches for weed suppression around trees. Bulk mulch is sold by the cubic yard; bagged mulch is usually 2 cubic feet. For edging beds with fencing, see the fence calculator.
Keep mulch a few inches clear of trunks and stems. Piling it against bark traps moisture and invites rot and pests, and it is the single most common mulching mistake. Material matters as well: fine shredded bark packs down and works at 2 inches, while chunky nuggets need closer to 3 inches to block light. Fluff and level an old layer before adding a new one so the bed does not creep steadily deeper each season. Water the bed before spreading so the mulch settles evenly instead of blowing around.
Frequently asked questions
- How do I calculate mulch?
- Multiply area in square feet by depth in inches, then divide by 324 to get cubic yards.
- How many bags of mulch in a cubic yard?
- A cubic yard is 27 cubic feet, so about 13.5 two-cubic-foot bags.
- How deep should mulch be?
- 2–3 inches for most beds; 3–4 inches for stronger weed suppression around trees and shrubs.
- Is bulk or bagged mulch cheaper?
- Bulk mulch by the cubic yard is usually cheaper for large areas; bags suit small jobs.
- How often should mulch be topped up?
- Once a year is typical, but measure what is already there and add only the difference. Layers deeper than about 4 inches stop water and air reaching the roots instead of helping them.