A layer of mulch on a planting bed helps suppress weeds, retain moisture, and moderate soil temperature. This Old House landscaping contractor Roger Cook recommends that planting beds be dressed in no more than three inches of mulch; lay down one inch a year, he says, then strip the beds every three years and start over. This keeps mulch from building up too deep, which prevents water and nutrients from reaching the roots.

It takes a surprising amount of mulch to dress a bed properly, so use this calculator before you head to the garden center. First you'll need to estimate the number of square feet to be covered. In a regular, rectangular bed, that's simply length times width: a 6-foot by 6-foot bed is 36 square feet. In an irregularly shaped bed, or for multiple small beds, you'll need to add up the areas of all the sections to be mulched.

Step 1

Step 2

How large an area, in square feet, do you need to cover?
(Choose one method, rounding up to nearest whole foot)

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