The formula to measure cubic feet is to multiply the length by the width. Then you take that sum and multiply it by the depth. A simple example is a sidewalk that is ten feet long, three feet wide and four inches deep. 10 times 3 equals 30 square feet. Multiply 30 times .333 and that equals 9.99 cubic feet. You can find more information here: http://www.onlineconversion.com/faq_01.htm
