Mulch Calculator

Plan mulch for one rectangular bed

Enter bed length and width in feet, finished depth in inches, and an extra allowance. Add the volume printed on one bag to estimate how many whole bags cover the adjusted volume.

From bed measurements to volume

Length multiplied by width gives square feet. Depth is divided by twelve to convert inches to feet, then multiplied by area for cubic feet. The extra percentage increases that base volume. Dividing adjusted cubic feet by 27 gives cubic yards, the unit commonly used for bulk landscape material.

Bag count always rounds up

A partial bag is normally purchased as a full bag, so the result divides adjusted volume by the entered bag size and rounds upward. Read the actual package volume rather than assuming every bag has the same size. Leave bag size empty when planning a bulk delivery instead.

Worked example

A 12-by-8-foot bed at 3 inches deep contains 24 cubic feet. Adding 10% produces 26.4 cubic feet, or about 0.98 cubic yard. With 2-cubic-foot bags, 13.2 bags are mathematically required, so the purchase estimate is 14 whole bags.

Measure beds without hiding gaps

For an irregular bed, split the space into smaller rectangles and calculate each separately. Subtract large areas occupied by patios, boulders, or dense structures only when they truly displace mulch. Existing mulch, settling, slopes, edging, and uneven ground can change the amount needed in the field.

Assumptions and limitations

This is a loose volume estimate, not landscaping, horticultural, drainage, or installation advice. It does not prescribe a safe depth, account for plant stems or tree trunks, model compaction and decomposition, price products, schedule delivery, or verify coverage claims. The extra allowance is editable planning arithmetic, not a recommendation. Confirm depth and product choice for the actual site.