When trees are cut down, the logs can be measured for their volume in order to be sold for furniture or firewood. Because logs are three-dimensional objects, the volume of the log can be measured in cubic feet. To calculate the volume of a log, you need to know the diameter and length of the log.
Use a measuring tape to measure the length and diameter of the log. The diameter is the distance from one side of the log, through the center, to the other side.
Divide the diameter of the log by two to calculate the radius of the log. For example, if the diameter of the log is 4 feet, you would divide 4 by 2 to get 2 feet for the radius.
Multiply the radius times the radius times 3.14 (pi) to calculate the area of the log's base. In this example, you would multiply 2 feet by 2 feet by 3.14 to find the area to be 12.56 square feet.
Multiply the area by the length to find the volume of the log. In this example, if the log was 15 feet long, you would multiply 12.56 square feet by 15 feet to get 188.4 cubic feet for the volume of the log.