Relevant range refers to a limited span of volume or activity. To illustrate, let's assume that a manufacturer's monthly production volume is consistently between 10,000 and 13,000 units and between 20,000 and 25,000 machine hours. Within this range of activity it operates smoothly with the same amount of monthly fixed costs (say $200,000) for supervisors, rent, depreciation, etc. If the volume were to drop below this range, the company would reduce the number of supervisors, the space rented, etc. so that its total monthly fixed costs would be smaller. If the volume exceeds the range, the company would incur additional fixed costs for more supervisors, space, etc. Hence, this company's relevant range of activity is 10,000 to 13,000 units of product or 20,000 to 25,000 machine hours. It is only in this relevant range that the monthly fixed costs are $200,000.