Mulch Calculator

Multiply your bed's area in square feet by the desired depth in inches (divided by 12 to convert to feet) to get cubic feet, then divide by 27 for cubic yards. A 100 sq ft bed at 3 inches deep needs 100 x (3/12) = 25 cubic feet, or about 0.93 cubic yards.

Bulk mulch by the cubic yard is more economical for large beds (typically anything over 200-300 sq ft) but requires delivery or a truck to haul it. Bagged mulch (usually 2 cubic feet per bag) is more convenient for smaller beds and easier to store leftover product.

At a standard 3-inch depth, 100 sq ft needs 25 cubic feet of mulch. Since a standard bag holds 2 cubic feet, that's 25 / 2 = 12.5, rounded up to 13 bags.

Most garden beds and landscaping do well with 2-4 inches of mulch. Around 2-3 inches works well for flower beds and around perennials, while 3-4 inches is common for tree rings, shrub beds, and weed suppression. Avoid piling mulch more than 4 inches deep or against tree trunks and stems, which can cause rot.

A standard mulch bag holds 2 cubic feet, and there are 27 cubic feet in a cubic yard, so one bag equals about 0.074 cubic yards. It takes roughly 13.5 bags to equal one full cubic yard.

Organic mulch (bark, wood chips) typically breaks down over 1-2 years and should be topped up annually or every other year with a fresh 1-2 inch layer, rather than removing and replacing the entire bed depth each time.

Yes, a mulch layer under about 2 inches often isn't thick enough to fully block weed growth, while a layer over 4 inches doesn't add much extra benefit and can actually harm plant roots by limiting oxygen and water penetration. 2-4 inches is the sweet spot.

Break the bed into smaller rectangular or triangular sections, calculate the square footage of each section separately, then add them together for the total area before applying the depth calculation.