Mulch Calculator

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. Since there's so much variation in coverage rates, you'll need to be sure to check the instructions on the seed you're buying to make sure you have enough. Some products require a pound for every 200 square feet of lawn; others will cover 1,000 square feet with just one pound of seed. Most coverage is expressed in a range, such as 350 to 500 square feet per pound (or about 2 to 3 pounds per 1,000 square feet). Always use the rate that provides the heaviest coverage if you're seeding a new lawn, and the lower rate if you're overseeding an existing lawn.

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.