Foundation Bed Mulch Calculator

The deduction is visible

For each straight run, subtract the clear band from the full bed width. Multiply the remaining width by the run length. Add the non-overlapping runs once, then multiply by the new layer depth. The worksheet shows the excluded area because a missing strip can make a purchase estimate too large.

Run area = length × (full bed width − clear band ÷ 12)
Mulch cubic feet = total run area × new depth in inches ÷ 12
Bulk cubic yards = cubic feet ÷ 27
Whole bags = round up (cubic feet ÷ printed bag cubic feet)

Example, not a preset: one 30 ft wall run with a 3 ft-wide bed and a user-selected 6 in clear band leaves 75 sq ft to mulch. A 2 in new layer takes 12.5 cu ft, or about 0.463 cu yd. A bag labeled 2 cu ft would mean 7 whole bags. These are arithmetic inputs, not a recommended depth, wall gap or order allowance.

Measure corners without counting ground twice

Use one row per straight strip of bed. If the bed wraps around a corner, stop the first run where the next run begins; do not include the same corner square in both lengths. For a curved bed or a bed with separate islands, use the curved-bed width worksheet or the measured-grid worksheet. This tool assumes a uniform new depth within each run; different depths belong in separate calculations.

Sources and boundaries

Iowa State University Extension's mulch guidance says mulch should be kept away from the house foundation and should not contact siding or cover windowsills. It does not supply one universal safe gap. A University of Maryland Extension response to a homeowner's foundation-bed question discusses a gap as site guidance, not a guarantee against pests. Iowa State's quantity guide supports area × depth and the cubic-foot, bag and cubic-yard conversions. This calculator uses only those arithmetic facts; it cannot assess a building's materials, drainage, pest risk or local code.