To determine the amount of soil, compost, mulch or plants needed for your garden, first calculate the square feet of the bed you are working with. Use the following calculation to determine the square feet of a bed that is 10 feet, 6 inches long and 4 feet wide. All units of measure need to be the same, so convert any measurements that are in inches to feet by dividing by 12 (inches in a foot). Multiply 10.5 feet in bed length by 4 feet in bed width, which equals 42 square feet of bed space.
